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1
2518-2521
, if f and g are continuous functions, then (f ± g) (x) = f (x) ± g(x) is continuous (f g) (x) = f (x) g(x) is continuous
1
2519-2522
(f g) (x) = f (x) g(x) is continuous ( ) ( ) ( ) f f x x g g x   =     (wherever g(x) ≠ 0) is continuous
1
2520-2523
g) (x) = f (x) g(x) is continuous ( ) ( ) ( ) f f x x g g x   =     (wherever g(x) ≠ 0) is continuous ® Every differentiable function is continuous, but the converse is not true
1
2521-2524
g(x) is continuous ( ) ( ) ( ) f f x x g g x   =     (wherever g(x) ≠ 0) is continuous ® Every differentiable function is continuous, but the converse is not true ® Chain rule is rule to differentiate composites of functions
1
2522-2525
( ) ( ) ( ) f f x x g g x   =     (wherever g(x) ≠ 0) is continuous ® Every differentiable function is continuous, but the converse is not true ® Chain rule is rule to differentiate composites of functions If f = v o u, t = u (x) and if both dt dx and dv dt exist then df dv dt dx =dt dx ⋅ ® Following are some of the standard derivatives (in appropriate domains): ( ) 1 2 1 sin 1 d x dx x − = − ( ) 1 2 1 cos 1 d x dx x − = − − ( ) 1 2 1 tan 1 d x dx x − = + ( x) x d e e dx = ( ) 1 log d x dx x = ® Logarithmic differentiation is a powerful technique to differentiate functions of the form f (x) = [u (x)]v (x)
1
2523-2526
® Every differentiable function is continuous, but the converse is not true ® Chain rule is rule to differentiate composites of functions If f = v o u, t = u (x) and if both dt dx and dv dt exist then df dv dt dx =dt dx ⋅ ® Following are some of the standard derivatives (in appropriate domains): ( ) 1 2 1 sin 1 d x dx x − = − ( ) 1 2 1 cos 1 d x dx x − = − − ( ) 1 2 1 tan 1 d x dx x − = + ( x) x d e e dx = ( ) 1 log d x dx x = ® Logarithmic differentiation is a powerful technique to differentiate functions of the form f (x) = [u (x)]v (x) Here both f (x) and u(x) need to be positive for this technique to make sense
1
2524-2527
® Chain rule is rule to differentiate composites of functions If f = v o u, t = u (x) and if both dt dx and dv dt exist then df dv dt dx =dt dx ⋅ ® Following are some of the standard derivatives (in appropriate domains): ( ) 1 2 1 sin 1 d x dx x − = − ( ) 1 2 1 cos 1 d x dx x − = − − ( ) 1 2 1 tan 1 d x dx x − = + ( x) x d e e dx = ( ) 1 log d x dx x = ® Logarithmic differentiation is a powerful technique to differentiate functions of the form f (x) = [u (x)]v (x) Here both f (x) and u(x) need to be positive for this technique to make sense —v v v v v— Rationalised 2023-24 v With the Calculus as a key, Mathematics can be successfully applied to the explanation of the course of Nature
1
2525-2528
If f = v o u, t = u (x) and if both dt dx and dv dt exist then df dv dt dx =dt dx ⋅ ® Following are some of the standard derivatives (in appropriate domains): ( ) 1 2 1 sin 1 d x dx x − = − ( ) 1 2 1 cos 1 d x dx x − = − − ( ) 1 2 1 tan 1 d x dx x − = + ( x) x d e e dx = ( ) 1 log d x dx x = ® Logarithmic differentiation is a powerful technique to differentiate functions of the form f (x) = [u (x)]v (x) Here both f (x) and u(x) need to be positive for this technique to make sense —v v v v v— Rationalised 2023-24 v With the Calculus as a key, Mathematics can be successfully applied to the explanation of the course of Nature ” — WHITEHEAD v 6
1
2526-2529
Here both f (x) and u(x) need to be positive for this technique to make sense —v v v v v— Rationalised 2023-24 v With the Calculus as a key, Mathematics can be successfully applied to the explanation of the course of Nature ” — WHITEHEAD v 6 1 Introduction In Chapter 5, we have learnt how to find derivative of composite functions, inverse trigonometric functions, implicit functions, exponential functions and logarithmic functions
1
2527-2530
—v v v v v— Rationalised 2023-24 v With the Calculus as a key, Mathematics can be successfully applied to the explanation of the course of Nature ” — WHITEHEAD v 6 1 Introduction In Chapter 5, we have learnt how to find derivative of composite functions, inverse trigonometric functions, implicit functions, exponential functions and logarithmic functions In this chapter, we will study applications of the derivative in various disciplines, e
1
2528-2531
” — WHITEHEAD v 6 1 Introduction In Chapter 5, we have learnt how to find derivative of composite functions, inverse trigonometric functions, implicit functions, exponential functions and logarithmic functions In this chapter, we will study applications of the derivative in various disciplines, e g
1
2529-2532
1 Introduction In Chapter 5, we have learnt how to find derivative of composite functions, inverse trigonometric functions, implicit functions, exponential functions and logarithmic functions In this chapter, we will study applications of the derivative in various disciplines, e g , in engineering, science, social science, and many other fields
1
2530-2533
In this chapter, we will study applications of the derivative in various disciplines, e g , in engineering, science, social science, and many other fields For instance, we will learn how the derivative can be used (i) to determine rate of change of quantities, (ii) to find the equations of tangent and normal to a curve at a point, (iii) to find turning points on the graph of a function which in turn will help us to locate points at which largest or smallest value (locally) of a function occurs
1
2531-2534
g , in engineering, science, social science, and many other fields For instance, we will learn how the derivative can be used (i) to determine rate of change of quantities, (ii) to find the equations of tangent and normal to a curve at a point, (iii) to find turning points on the graph of a function which in turn will help us to locate points at which largest or smallest value (locally) of a function occurs We will also use derivative to find intervals on which a function is increasing or decreasing
1
2532-2535
, in engineering, science, social science, and many other fields For instance, we will learn how the derivative can be used (i) to determine rate of change of quantities, (ii) to find the equations of tangent and normal to a curve at a point, (iii) to find turning points on the graph of a function which in turn will help us to locate points at which largest or smallest value (locally) of a function occurs We will also use derivative to find intervals on which a function is increasing or decreasing Finally, we use the derivative to find approximate value of certain quantities
1
2533-2536
For instance, we will learn how the derivative can be used (i) to determine rate of change of quantities, (ii) to find the equations of tangent and normal to a curve at a point, (iii) to find turning points on the graph of a function which in turn will help us to locate points at which largest or smallest value (locally) of a function occurs We will also use derivative to find intervals on which a function is increasing or decreasing Finally, we use the derivative to find approximate value of certain quantities 6
1
2534-2537
We will also use derivative to find intervals on which a function is increasing or decreasing Finally, we use the derivative to find approximate value of certain quantities 6 2 Rate of Change of Quantities Recall that by the derivative ds dt , we mean the rate of change of distance s with respect to the time t
1
2535-2538
Finally, we use the derivative to find approximate value of certain quantities 6 2 Rate of Change of Quantities Recall that by the derivative ds dt , we mean the rate of change of distance s with respect to the time t In a similar fashion, whenever one quantity y varies with another quantity x, satisfying some rule ( ) y =f x , then dy dx (or f′(x)) represents the rate of change of y with respect to x and dy dx x x  = 0 (or f′(x0)) represents the rate of change of y with respect to x at 0 x =x
1
2536-2539
6 2 Rate of Change of Quantities Recall that by the derivative ds dt , we mean the rate of change of distance s with respect to the time t In a similar fashion, whenever one quantity y varies with another quantity x, satisfying some rule ( ) y =f x , then dy dx (or f′(x)) represents the rate of change of y with respect to x and dy dx x x  = 0 (or f′(x0)) represents the rate of change of y with respect to x at 0 x =x if Further, if two variables x and y are varying with respect to another variable t, i
1
2537-2540
2 Rate of Change of Quantities Recall that by the derivative ds dt , we mean the rate of change of distance s with respect to the time t In a similar fashion, whenever one quantity y varies with another quantity x, satisfying some rule ( ) y =f x , then dy dx (or f′(x)) represents the rate of change of y with respect to x and dy dx x x  = 0 (or f′(x0)) represents the rate of change of y with respect to x at 0 x =x if Further, if two variables x and y are varying with respect to another variable t, i e
1
2538-2541
In a similar fashion, whenever one quantity y varies with another quantity x, satisfying some rule ( ) y =f x , then dy dx (or f′(x)) represents the rate of change of y with respect to x and dy dx x x  = 0 (or f′(x0)) represents the rate of change of y with respect to x at 0 x =x if Further, if two variables x and y are varying with respect to another variable t, i e , ( ) x =f t and ( ) y =g t , then by Chain Rule dy dx = dy dx dt dt , if 0 dx dt ≠ Chapter 6 APPLICATION OF DERIVATIVES Rationalised 2023-24 MATHEMATICS 148 Thus, the rate of change of y with respect to x can be calculated using the rate of change of y and that of x both with respect to t
1
2539-2542
if Further, if two variables x and y are varying with respect to another variable t, i e , ( ) x =f t and ( ) y =g t , then by Chain Rule dy dx = dy dx dt dt , if 0 dx dt ≠ Chapter 6 APPLICATION OF DERIVATIVES Rationalised 2023-24 MATHEMATICS 148 Thus, the rate of change of y with respect to x can be calculated using the rate of change of y and that of x both with respect to t Let us consider some examples
1
2540-2543
e , ( ) x =f t and ( ) y =g t , then by Chain Rule dy dx = dy dx dt dt , if 0 dx dt ≠ Chapter 6 APPLICATION OF DERIVATIVES Rationalised 2023-24 MATHEMATICS 148 Thus, the rate of change of y with respect to x can be calculated using the rate of change of y and that of x both with respect to t Let us consider some examples Example 1 Find the rate of change of the area of a circle per second with respect to its radius r when r = 5 cm
1
2541-2544
, ( ) x =f t and ( ) y =g t , then by Chain Rule dy dx = dy dx dt dt , if 0 dx dt ≠ Chapter 6 APPLICATION OF DERIVATIVES Rationalised 2023-24 MATHEMATICS 148 Thus, the rate of change of y with respect to x can be calculated using the rate of change of y and that of x both with respect to t Let us consider some examples Example 1 Find the rate of change of the area of a circle per second with respect to its radius r when r = 5 cm Solution The area A of a circle with radius r is given by A = πr2
1
2542-2545
Let us consider some examples Example 1 Find the rate of change of the area of a circle per second with respect to its radius r when r = 5 cm Solution The area A of a circle with radius r is given by A = πr2 Therefore, the rate of change of the area A with respect to its radius r is given by 2 A ( ) 2 d d r r dr =dr π = π
1
2543-2546
Example 1 Find the rate of change of the area of a circle per second with respect to its radius r when r = 5 cm Solution The area A of a circle with radius r is given by A = πr2 Therefore, the rate of change of the area A with respect to its radius r is given by 2 A ( ) 2 d d r r dr =dr π = π When r = 5 cm, A 10 d dr = π
1
2544-2547
Solution The area A of a circle with radius r is given by A = πr2 Therefore, the rate of change of the area A with respect to its radius r is given by 2 A ( ) 2 d d r r dr =dr π = π When r = 5 cm, A 10 d dr = π Thus, the area of the circle is changing at the rate of 10π cm2/s
1
2545-2548
Therefore, the rate of change of the area A with respect to its radius r is given by 2 A ( ) 2 d d r r dr =dr π = π When r = 5 cm, A 10 d dr = π Thus, the area of the circle is changing at the rate of 10π cm2/s Example 2 The volume of a cube is increasing at a rate of 9 cubic centimetres per second
1
2546-2549
When r = 5 cm, A 10 d dr = π Thus, the area of the circle is changing at the rate of 10π cm2/s Example 2 The volume of a cube is increasing at a rate of 9 cubic centimetres per second How fast is the surface area increasing when the length of an edge is 10 centimetres
1
2547-2550
Thus, the area of the circle is changing at the rate of 10π cm2/s Example 2 The volume of a cube is increasing at a rate of 9 cubic centimetres per second How fast is the surface area increasing when the length of an edge is 10 centimetres Solution Let x be the length of a side, V be the volume and S be the surface area of the cube
1
2548-2551
Example 2 The volume of a cube is increasing at a rate of 9 cubic centimetres per second How fast is the surface area increasing when the length of an edge is 10 centimetres Solution Let x be the length of a side, V be the volume and S be the surface area of the cube Then, V = x3 and S = 6x2, where x is a function of time t
1
2549-2552
How fast is the surface area increasing when the length of an edge is 10 centimetres Solution Let x be the length of a side, V be the volume and S be the surface area of the cube Then, V = x3 and S = 6x2, where x is a function of time t Now dV dt = 9cm3/s (Given) Therefore 9 = 3 3 V ( ) ( ) d d d dx x x dt dt dx dt = = ⋅ (By Chain Rule) = 32 dx x dt ⋅ or dx dt = x32
1
2550-2553
Solution Let x be the length of a side, V be the volume and S be the surface area of the cube Then, V = x3 and S = 6x2, where x is a function of time t Now dV dt = 9cm3/s (Given) Therefore 9 = 3 3 V ( ) ( ) d d d dx x x dt dt dx dt = = ⋅ (By Chain Rule) = 32 dx x dt ⋅ or dx dt = x32 (1) Now dS dt = 2 2 (6 ) (6 ) d d dx x x dt dx dt = ⋅ (By Chain Rule) = 32 36 12x x x  ⋅ =     (Using (1)) Hence, when x = 10 cm, 2 3
1
2551-2554
Then, V = x3 and S = 6x2, where x is a function of time t Now dV dt = 9cm3/s (Given) Therefore 9 = 3 3 V ( ) ( ) d d d dx x x dt dt dx dt = = ⋅ (By Chain Rule) = 32 dx x dt ⋅ or dx dt = x32 (1) Now dS dt = 2 2 (6 ) (6 ) d d dx x x dt dx dt = ⋅ (By Chain Rule) = 32 36 12x x x  ⋅ =     (Using (1)) Hence, when x = 10 cm, 2 3 6 cm /s dS dt = Rationalised 2023-24 APPLICATION OF DERIVATIVES 149 Example 3 A stone is dropped into a quiet lake and waves move in circles at a speed of 4cm per second
1
2552-2555
Now dV dt = 9cm3/s (Given) Therefore 9 = 3 3 V ( ) ( ) d d d dx x x dt dt dx dt = = ⋅ (By Chain Rule) = 32 dx x dt ⋅ or dx dt = x32 (1) Now dS dt = 2 2 (6 ) (6 ) d d dx x x dt dx dt = ⋅ (By Chain Rule) = 32 36 12x x x  ⋅ =     (Using (1)) Hence, when x = 10 cm, 2 3 6 cm /s dS dt = Rationalised 2023-24 APPLICATION OF DERIVATIVES 149 Example 3 A stone is dropped into a quiet lake and waves move in circles at a speed of 4cm per second At the instant, when the radius of the circular wave is 10 cm, how fast is the enclosed area increasing
1
2553-2556
(1) Now dS dt = 2 2 (6 ) (6 ) d d dx x x dt dx dt = ⋅ (By Chain Rule) = 32 36 12x x x  ⋅ =     (Using (1)) Hence, when x = 10 cm, 2 3 6 cm /s dS dt = Rationalised 2023-24 APPLICATION OF DERIVATIVES 149 Example 3 A stone is dropped into a quiet lake and waves move in circles at a speed of 4cm per second At the instant, when the radius of the circular wave is 10 cm, how fast is the enclosed area increasing Solution The area A of a circle with radius r is given by A = πr2
1
2554-2557
6 cm /s dS dt = Rationalised 2023-24 APPLICATION OF DERIVATIVES 149 Example 3 A stone is dropped into a quiet lake and waves move in circles at a speed of 4cm per second At the instant, when the radius of the circular wave is 10 cm, how fast is the enclosed area increasing Solution The area A of a circle with radius r is given by A = πr2 Therefore, the rate of change of area A with respect to time t is dA dt = 2 2 ( ) ( ) d d dr r r dt dr dt π = π ⋅ = 2π r dr dt (By Chain Rule) It is given that dr dt = 4cm/s Therefore, when r = 10 cm, dA dt = 2π(10) (4) = 80π Thus, the enclosed area is increasing at the rate of 80π cm2/s, when r = 10 cm
1
2555-2558
At the instant, when the radius of the circular wave is 10 cm, how fast is the enclosed area increasing Solution The area A of a circle with radius r is given by A = πr2 Therefore, the rate of change of area A with respect to time t is dA dt = 2 2 ( ) ( ) d d dr r r dt dr dt π = π ⋅ = 2π r dr dt (By Chain Rule) It is given that dr dt = 4cm/s Therefore, when r = 10 cm, dA dt = 2π(10) (4) = 80π Thus, the enclosed area is increasing at the rate of 80π cm2/s, when r = 10 cm ANote dy dx is positive if y increases as x increases and is negative if y decreases as x increases
1
2556-2559
Solution The area A of a circle with radius r is given by A = πr2 Therefore, the rate of change of area A with respect to time t is dA dt = 2 2 ( ) ( ) d d dr r r dt dr dt π = π ⋅ = 2π r dr dt (By Chain Rule) It is given that dr dt = 4cm/s Therefore, when r = 10 cm, dA dt = 2π(10) (4) = 80π Thus, the enclosed area is increasing at the rate of 80π cm2/s, when r = 10 cm ANote dy dx is positive if y increases as x increases and is negative if y decreases as x increases Example 4 The length x of a rectangle is decreasing at the rate of 3 cm/minute and the width y is increasing at the rate of 2cm/minute
1
2557-2560
Therefore, the rate of change of area A with respect to time t is dA dt = 2 2 ( ) ( ) d d dr r r dt dr dt π = π ⋅ = 2π r dr dt (By Chain Rule) It is given that dr dt = 4cm/s Therefore, when r = 10 cm, dA dt = 2π(10) (4) = 80π Thus, the enclosed area is increasing at the rate of 80π cm2/s, when r = 10 cm ANote dy dx is positive if y increases as x increases and is negative if y decreases as x increases Example 4 The length x of a rectangle is decreasing at the rate of 3 cm/minute and the width y is increasing at the rate of 2cm/minute When x =10cm and y = 6cm, find the rates of change of (a) the perimeter and (b) the area of the rectangle
1
2558-2561
ANote dy dx is positive if y increases as x increases and is negative if y decreases as x increases Example 4 The length x of a rectangle is decreasing at the rate of 3 cm/minute and the width y is increasing at the rate of 2cm/minute When x =10cm and y = 6cm, find the rates of change of (a) the perimeter and (b) the area of the rectangle Solution Since the length x is decreasing and the width y is increasing with respect to time, we have 3 cm/min dx dt = − and 2 cm/min dy dt = (a) The perimeter P of a rectangle is given by P = 2 (x + y) Therefore dP dt = 2 2 3 2 2 dx dt dy +dt    = − + = − ( ) cm/min (b) The area A of the rectangle is given by A = x
1
2559-2562
Example 4 The length x of a rectangle is decreasing at the rate of 3 cm/minute and the width y is increasing at the rate of 2cm/minute When x =10cm and y = 6cm, find the rates of change of (a) the perimeter and (b) the area of the rectangle Solution Since the length x is decreasing and the width y is increasing with respect to time, we have 3 cm/min dx dt = − and 2 cm/min dy dt = (a) The perimeter P of a rectangle is given by P = 2 (x + y) Therefore dP dt = 2 2 3 2 2 dx dt dy +dt    = − + = − ( ) cm/min (b) The area A of the rectangle is given by A = x y Therefore dA dt = dx dy y x dt dt ⋅ + ⋅ = – 3(6) + 10(2) (as x = 10 cm and y = 6 cm) = 2 cm2/min Rationalised 2023-24 MATHEMATICS 150 Example 5 The total cost C(x) in Rupees, associated with the production of x units of an item is given by C(x) = 0
1
2560-2563
When x =10cm and y = 6cm, find the rates of change of (a) the perimeter and (b) the area of the rectangle Solution Since the length x is decreasing and the width y is increasing with respect to time, we have 3 cm/min dx dt = − and 2 cm/min dy dt = (a) The perimeter P of a rectangle is given by P = 2 (x + y) Therefore dP dt = 2 2 3 2 2 dx dt dy +dt    = − + = − ( ) cm/min (b) The area A of the rectangle is given by A = x y Therefore dA dt = dx dy y x dt dt ⋅ + ⋅ = – 3(6) + 10(2) (as x = 10 cm and y = 6 cm) = 2 cm2/min Rationalised 2023-24 MATHEMATICS 150 Example 5 The total cost C(x) in Rupees, associated with the production of x units of an item is given by C(x) = 0 005 x3 – 0
1
2561-2564
Solution Since the length x is decreasing and the width y is increasing with respect to time, we have 3 cm/min dx dt = − and 2 cm/min dy dt = (a) The perimeter P of a rectangle is given by P = 2 (x + y) Therefore dP dt = 2 2 3 2 2 dx dt dy +dt    = − + = − ( ) cm/min (b) The area A of the rectangle is given by A = x y Therefore dA dt = dx dy y x dt dt ⋅ + ⋅ = – 3(6) + 10(2) (as x = 10 cm and y = 6 cm) = 2 cm2/min Rationalised 2023-24 MATHEMATICS 150 Example 5 The total cost C(x) in Rupees, associated with the production of x units of an item is given by C(x) = 0 005 x3 – 0 02 x2 + 30x + 5000 Find the marginal cost when 3 units are produced, where by marginal cost we mean the instantaneous rate of change of total cost at any level of output
1
2562-2565
y Therefore dA dt = dx dy y x dt dt ⋅ + ⋅ = – 3(6) + 10(2) (as x = 10 cm and y = 6 cm) = 2 cm2/min Rationalised 2023-24 MATHEMATICS 150 Example 5 The total cost C(x) in Rupees, associated with the production of x units of an item is given by C(x) = 0 005 x3 – 0 02 x2 + 30x + 5000 Find the marginal cost when 3 units are produced, where by marginal cost we mean the instantaneous rate of change of total cost at any level of output Solution Since marginal cost is the rate of change of total cost with respect to the output, we have Marginal cost (MC) = 0
1
2563-2566
005 x3 – 0 02 x2 + 30x + 5000 Find the marginal cost when 3 units are produced, where by marginal cost we mean the instantaneous rate of change of total cost at any level of output Solution Since marginal cost is the rate of change of total cost with respect to the output, we have Marginal cost (MC) = 0 005(32 ) 0
1
2564-2567
02 x2 + 30x + 5000 Find the marginal cost when 3 units are produced, where by marginal cost we mean the instantaneous rate of change of total cost at any level of output Solution Since marginal cost is the rate of change of total cost with respect to the output, we have Marginal cost (MC) = 0 005(32 ) 0 02(2 ) 30 dC x x dx = − + When x = 3, MC = 0
1
2565-2568
Solution Since marginal cost is the rate of change of total cost with respect to the output, we have Marginal cost (MC) = 0 005(32 ) 0 02(2 ) 30 dC x x dx = − + When x = 3, MC = 0 015(3 )2 0
1
2566-2569
005(32 ) 0 02(2 ) 30 dC x x dx = − + When x = 3, MC = 0 015(3 )2 0 04(3) 30 − + = 0
1
2567-2570
02(2 ) 30 dC x x dx = − + When x = 3, MC = 0 015(3 )2 0 04(3) 30 − + = 0 135 – 0
1
2568-2571
015(3 )2 0 04(3) 30 − + = 0 135 – 0 12 + 30 = 30
1
2569-2572
04(3) 30 − + = 0 135 – 0 12 + 30 = 30 015 Hence, the required marginal cost is ` 30
1
2570-2573
135 – 0 12 + 30 = 30 015 Hence, the required marginal cost is ` 30 02 (nearly)
1
2571-2574
12 + 30 = 30 015 Hence, the required marginal cost is ` 30 02 (nearly) Example 6 The total revenue in Rupees received from the sale of x units of a product is given by R(x) = 3x2 + 36x + 5
1
2572-2575
015 Hence, the required marginal cost is ` 30 02 (nearly) Example 6 The total revenue in Rupees received from the sale of x units of a product is given by R(x) = 3x2 + 36x + 5 Find the marginal revenue, when x = 5, where by marginal revenue we mean the rate of change of total revenue with respect to the number of items sold at an instant
1
2573-2576
02 (nearly) Example 6 The total revenue in Rupees received from the sale of x units of a product is given by R(x) = 3x2 + 36x + 5 Find the marginal revenue, when x = 5, where by marginal revenue we mean the rate of change of total revenue with respect to the number of items sold at an instant Solution Since marginal revenue is the rate of change of total revenue with respect to the number of units sold, we have Marginal Revenue (MR) = R 6 36 d dx =x + When x = 5, MR = 6(5) + 36 = 66 Hence, the required marginal revenue is ` 66
1
2574-2577
Example 6 The total revenue in Rupees received from the sale of x units of a product is given by R(x) = 3x2 + 36x + 5 Find the marginal revenue, when x = 5, where by marginal revenue we mean the rate of change of total revenue with respect to the number of items sold at an instant Solution Since marginal revenue is the rate of change of total revenue with respect to the number of units sold, we have Marginal Revenue (MR) = R 6 36 d dx =x + When x = 5, MR = 6(5) + 36 = 66 Hence, the required marginal revenue is ` 66 EXERCISE 6
1
2575-2578
Find the marginal revenue, when x = 5, where by marginal revenue we mean the rate of change of total revenue with respect to the number of items sold at an instant Solution Since marginal revenue is the rate of change of total revenue with respect to the number of units sold, we have Marginal Revenue (MR) = R 6 36 d dx =x + When x = 5, MR = 6(5) + 36 = 66 Hence, the required marginal revenue is ` 66 EXERCISE 6 1 1
1
2576-2579
Solution Since marginal revenue is the rate of change of total revenue with respect to the number of units sold, we have Marginal Revenue (MR) = R 6 36 d dx =x + When x = 5, MR = 6(5) + 36 = 66 Hence, the required marginal revenue is ` 66 EXERCISE 6 1 1 Find the rate of change of the area of a circle with respect to its radius r when (a) r = 3 cm (b) r = 4 cm 2
1
2577-2580
EXERCISE 6 1 1 Find the rate of change of the area of a circle with respect to its radius r when (a) r = 3 cm (b) r = 4 cm 2 The volume of a cube is increasing at the rate of 8 cm3/s
1
2578-2581
1 1 Find the rate of change of the area of a circle with respect to its radius r when (a) r = 3 cm (b) r = 4 cm 2 The volume of a cube is increasing at the rate of 8 cm3/s How fast is the surface area increasing when the length of an edge is 12 cm
1
2579-2582
Find the rate of change of the area of a circle with respect to its radius r when (a) r = 3 cm (b) r = 4 cm 2 The volume of a cube is increasing at the rate of 8 cm3/s How fast is the surface area increasing when the length of an edge is 12 cm 3
1
2580-2583
The volume of a cube is increasing at the rate of 8 cm3/s How fast is the surface area increasing when the length of an edge is 12 cm 3 The radius of a circle is increasing uniformly at the rate of 3 cm/s
1
2581-2584
How fast is the surface area increasing when the length of an edge is 12 cm 3 The radius of a circle is increasing uniformly at the rate of 3 cm/s Find the rate at which the area of the circle is increasing when the radius is 10 cm
1
2582-2585
3 The radius of a circle is increasing uniformly at the rate of 3 cm/s Find the rate at which the area of the circle is increasing when the radius is 10 cm 4
1
2583-2586
The radius of a circle is increasing uniformly at the rate of 3 cm/s Find the rate at which the area of the circle is increasing when the radius is 10 cm 4 An edge of a variable cube is increasing at the rate of 3 cm/s
1
2584-2587
Find the rate at which the area of the circle is increasing when the radius is 10 cm 4 An edge of a variable cube is increasing at the rate of 3 cm/s How fast is the volume of the cube increasing when the edge is 10 cm long
1
2585-2588
4 An edge of a variable cube is increasing at the rate of 3 cm/s How fast is the volume of the cube increasing when the edge is 10 cm long 5
1
2586-2589
An edge of a variable cube is increasing at the rate of 3 cm/s How fast is the volume of the cube increasing when the edge is 10 cm long 5 A stone is dropped into a quiet lake and waves move in circles at the speed of 5 cm/s
1
2587-2590
How fast is the volume of the cube increasing when the edge is 10 cm long 5 A stone is dropped into a quiet lake and waves move in circles at the speed of 5 cm/s At the instant when the radius of the circular wave is 8 cm, how fast is the enclosed area increasing
1
2588-2591
5 A stone is dropped into a quiet lake and waves move in circles at the speed of 5 cm/s At the instant when the radius of the circular wave is 8 cm, how fast is the enclosed area increasing Rationalised 2023-24 APPLICATION OF DERIVATIVES 151 6
1
2589-2592
A stone is dropped into a quiet lake and waves move in circles at the speed of 5 cm/s At the instant when the radius of the circular wave is 8 cm, how fast is the enclosed area increasing Rationalised 2023-24 APPLICATION OF DERIVATIVES 151 6 The radius of a circle is increasing at the rate of 0
1
2590-2593
At the instant when the radius of the circular wave is 8 cm, how fast is the enclosed area increasing Rationalised 2023-24 APPLICATION OF DERIVATIVES 151 6 The radius of a circle is increasing at the rate of 0 7 cm/s
1
2591-2594
Rationalised 2023-24 APPLICATION OF DERIVATIVES 151 6 The radius of a circle is increasing at the rate of 0 7 cm/s What is the rate of increase of its circumference
1
2592-2595
The radius of a circle is increasing at the rate of 0 7 cm/s What is the rate of increase of its circumference 7
1
2593-2596
7 cm/s What is the rate of increase of its circumference 7 The length x of a rectangle is decreasing at the rate of 5 cm/minute and the width y is increasing at the rate of 4 cm/minute
1
2594-2597
What is the rate of increase of its circumference 7 The length x of a rectangle is decreasing at the rate of 5 cm/minute and the width y is increasing at the rate of 4 cm/minute When x = 8cm and y = 6cm, find the rates of change of (a) the perimeter, and (b) the area of the rectangle
1
2595-2598
7 The length x of a rectangle is decreasing at the rate of 5 cm/minute and the width y is increasing at the rate of 4 cm/minute When x = 8cm and y = 6cm, find the rates of change of (a) the perimeter, and (b) the area of the rectangle 8
1
2596-2599
The length x of a rectangle is decreasing at the rate of 5 cm/minute and the width y is increasing at the rate of 4 cm/minute When x = 8cm and y = 6cm, find the rates of change of (a) the perimeter, and (b) the area of the rectangle 8 A balloon, which always remains spherical on inflation, is being inflated by pumping in 900 cubic centimetres of gas per second
1
2597-2600
When x = 8cm and y = 6cm, find the rates of change of (a) the perimeter, and (b) the area of the rectangle 8 A balloon, which always remains spherical on inflation, is being inflated by pumping in 900 cubic centimetres of gas per second Find the rate at which the radius of the balloon increases when the radius is 15 cm
1
2598-2601
8 A balloon, which always remains spherical on inflation, is being inflated by pumping in 900 cubic centimetres of gas per second Find the rate at which the radius of the balloon increases when the radius is 15 cm 9
1
2599-2602
A balloon, which always remains spherical on inflation, is being inflated by pumping in 900 cubic centimetres of gas per second Find the rate at which the radius of the balloon increases when the radius is 15 cm 9 A balloon, which always remains spherical has a variable radius
1
2600-2603
Find the rate at which the radius of the balloon increases when the radius is 15 cm 9 A balloon, which always remains spherical has a variable radius Find the rate at which its volume is increasing with the radius when the later is 10 cm
1
2601-2604
9 A balloon, which always remains spherical has a variable radius Find the rate at which its volume is increasing with the radius when the later is 10 cm 10
1
2602-2605
A balloon, which always remains spherical has a variable radius Find the rate at which its volume is increasing with the radius when the later is 10 cm 10 A ladder 5 m long is leaning against a wall
1
2603-2606
Find the rate at which its volume is increasing with the radius when the later is 10 cm 10 A ladder 5 m long is leaning against a wall The bottom of the ladder is pulled along the ground, away from the wall, at the rate of 2cm/s
1
2604-2607
10 A ladder 5 m long is leaning against a wall The bottom of the ladder is pulled along the ground, away from the wall, at the rate of 2cm/s How fast is its height on the wall decreasing when the foot of the ladder is 4 m away from the wall
1
2605-2608
A ladder 5 m long is leaning against a wall The bottom of the ladder is pulled along the ground, away from the wall, at the rate of 2cm/s How fast is its height on the wall decreasing when the foot of the ladder is 4 m away from the wall 11
1
2606-2609
The bottom of the ladder is pulled along the ground, away from the wall, at the rate of 2cm/s How fast is its height on the wall decreasing when the foot of the ladder is 4 m away from the wall 11 A particle moves along the curve 6y = x3 +2
1
2607-2610
How fast is its height on the wall decreasing when the foot of the ladder is 4 m away from the wall 11 A particle moves along the curve 6y = x3 +2 Find the points on the curve at which the y-coordinate is changing 8 times as fast as the x-coordinate
1
2608-2611
11 A particle moves along the curve 6y = x3 +2 Find the points on the curve at which the y-coordinate is changing 8 times as fast as the x-coordinate 12
1
2609-2612
A particle moves along the curve 6y = x3 +2 Find the points on the curve at which the y-coordinate is changing 8 times as fast as the x-coordinate 12 The radius of an air bubble is increasing at the rate of 1 2 cm/s
1
2610-2613
Find the points on the curve at which the y-coordinate is changing 8 times as fast as the x-coordinate 12 The radius of an air bubble is increasing at the rate of 1 2 cm/s At what rate is the volume of the bubble increasing when the radius is 1 cm
1
2611-2614
12 The radius of an air bubble is increasing at the rate of 1 2 cm/s At what rate is the volume of the bubble increasing when the radius is 1 cm 13
1
2612-2615
The radius of an air bubble is increasing at the rate of 1 2 cm/s At what rate is the volume of the bubble increasing when the radius is 1 cm 13 A balloon, which always remains spherical, has a variable diameter 3 (2 1) 2 x +
1
2613-2616
At what rate is the volume of the bubble increasing when the radius is 1 cm 13 A balloon, which always remains spherical, has a variable diameter 3 (2 1) 2 x + Find the rate of change of its volume with respect to x
1
2614-2617
13 A balloon, which always remains spherical, has a variable diameter 3 (2 1) 2 x + Find the rate of change of its volume with respect to x 14
1
2615-2618
A balloon, which always remains spherical, has a variable diameter 3 (2 1) 2 x + Find the rate of change of its volume with respect to x 14 Sand is pouring from a pipe at the rate of 12 cm3/s
1
2616-2619
Find the rate of change of its volume with respect to x 14 Sand is pouring from a pipe at the rate of 12 cm3/s The falling sand forms a cone on the ground in such a way that the height of the cone is always one-sixth of the radius of the base
1
2617-2620
14 Sand is pouring from a pipe at the rate of 12 cm3/s The falling sand forms a cone on the ground in such a way that the height of the cone is always one-sixth of the radius of the base How fast is the height of the sand cone increasing when the height is 4 cm