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1
3018-3021
The value of f at this point is given by f (1) = (1 – 3)2 + (1)4 = 5 Thus, the distance between the solider and the helicopter is (1) 5 f = Note that 5 is either a maximum value or a minimum value Since f(0) = 2 4 (0 3) (0) 3 5 − + = > , it follows that 5 is the minimum value of ( ) f x
1
3019-3022
Thus, the distance between the solider and the helicopter is (1) 5 f = Note that 5 is either a maximum value or a minimum value Since f(0) = 2 4 (0 3) (0) 3 5 − + = > , it follows that 5 is the minimum value of ( ) f x Hence, 5 is the minimum distance between the soldier and the helicopter
1
3020-3023
Note that 5 is either a maximum value or a minimum value Since f(0) = 2 4 (0 3) (0) 3 5 − + = > , it follows that 5 is the minimum value of ( ) f x Hence, 5 is the minimum distance between the soldier and the helicopter EXERCISE 6
1
3021-3024
Since f(0) = 2 4 (0 3) (0) 3 5 − + = > , it follows that 5 is the minimum value of ( ) f x Hence, 5 is the minimum distance between the soldier and the helicopter EXERCISE 6 3 1
1
3022-3025
Hence, 5 is the minimum distance between the soldier and the helicopter EXERCISE 6 3 1 Find the maximum and minimum values, if any, of the following functions given by (i) f (x) = (2x – 1)2 + 3 (ii) f (x) = 9x2 + 12x + 2 (iii) f (x) = – (x – 1)2 + 10 (iv) g(x) = x3 + 1 Rationalised 2023-24 APPLICATION OF DERIVATIVES 175 2
1
3023-3026
EXERCISE 6 3 1 Find the maximum and minimum values, if any, of the following functions given by (i) f (x) = (2x – 1)2 + 3 (ii) f (x) = 9x2 + 12x + 2 (iii) f (x) = – (x – 1)2 + 10 (iv) g(x) = x3 + 1 Rationalised 2023-24 APPLICATION OF DERIVATIVES 175 2 Find the maximum and minimum values, if any, of the following functions given by (i) f (x) = |x + 2| – 1 (ii) g(x) = – |x + 1| + 3 (iii) h(x) = sin(2x) + 5 (iv) f (x) = |sin 4x + 3| (v) h(x) = x + 1, x ∈ (– 1, 1) 3
1
3024-3027
3 1 Find the maximum and minimum values, if any, of the following functions given by (i) f (x) = (2x – 1)2 + 3 (ii) f (x) = 9x2 + 12x + 2 (iii) f (x) = – (x – 1)2 + 10 (iv) g(x) = x3 + 1 Rationalised 2023-24 APPLICATION OF DERIVATIVES 175 2 Find the maximum and minimum values, if any, of the following functions given by (i) f (x) = |x + 2| – 1 (ii) g(x) = – |x + 1| + 3 (iii) h(x) = sin(2x) + 5 (iv) f (x) = |sin 4x + 3| (v) h(x) = x + 1, x ∈ (– 1, 1) 3 Find the local maxima and local minima, if any, of the following functions
1
3025-3028
Find the maximum and minimum values, if any, of the following functions given by (i) f (x) = (2x – 1)2 + 3 (ii) f (x) = 9x2 + 12x + 2 (iii) f (x) = – (x – 1)2 + 10 (iv) g(x) = x3 + 1 Rationalised 2023-24 APPLICATION OF DERIVATIVES 175 2 Find the maximum and minimum values, if any, of the following functions given by (i) f (x) = |x + 2| – 1 (ii) g(x) = – |x + 1| + 3 (iii) h(x) = sin(2x) + 5 (iv) f (x) = |sin 4x + 3| (v) h(x) = x + 1, x ∈ (– 1, 1) 3 Find the local maxima and local minima, if any, of the following functions Find also the local maximum and the local minimum values, as the case may be: (i) f (x) = x2 (ii) g(x) = x3 – 3x (iii) h(x) = sin x + cos x, 0 2 x π < < (iv) f (x) = sin x – cos x, 0 2 <x < π (v) f (x) = x3 – 6x2 + 9x + 15 (vi) 2 ( ) , 0 x2 g x x x = + > (vii) 2 1 ( ) 2 g x x = + (viii) ( ) 1 , 0 1 = − < < f x x x x 4
1
3026-3029
Find the maximum and minimum values, if any, of the following functions given by (i) f (x) = |x + 2| – 1 (ii) g(x) = – |x + 1| + 3 (iii) h(x) = sin(2x) + 5 (iv) f (x) = |sin 4x + 3| (v) h(x) = x + 1, x ∈ (– 1, 1) 3 Find the local maxima and local minima, if any, of the following functions Find also the local maximum and the local minimum values, as the case may be: (i) f (x) = x2 (ii) g(x) = x3 – 3x (iii) h(x) = sin x + cos x, 0 2 x π < < (iv) f (x) = sin x – cos x, 0 2 <x < π (v) f (x) = x3 – 6x2 + 9x + 15 (vi) 2 ( ) , 0 x2 g x x x = + > (vii) 2 1 ( ) 2 g x x = + (viii) ( ) 1 , 0 1 = − < < f x x x x 4 Prove that the following functions do not have maxima or minima: (i) f (x) = ex (ii) g(x) = log x (iii) h (x) = x3 + x2 + x +1 5
1
3027-3030
Find the local maxima and local minima, if any, of the following functions Find also the local maximum and the local minimum values, as the case may be: (i) f (x) = x2 (ii) g(x) = x3 – 3x (iii) h(x) = sin x + cos x, 0 2 x π < < (iv) f (x) = sin x – cos x, 0 2 <x < π (v) f (x) = x3 – 6x2 + 9x + 15 (vi) 2 ( ) , 0 x2 g x x x = + > (vii) 2 1 ( ) 2 g x x = + (viii) ( ) 1 , 0 1 = − < < f x x x x 4 Prove that the following functions do not have maxima or minima: (i) f (x) = ex (ii) g(x) = log x (iii) h (x) = x3 + x2 + x +1 5 Find the absolute maximum value and the absolute minimum value of the following functions in the given intervals: (i) f (x) = x3, x ∈ [– 2, 2] (ii) f (x) = sin x + cos x , x ∈ [0, π] (iii) f (x) = 12 9 4 , 2, 2 2 x x x   − ∈ −     (iv) 2 ( ) ( 1) 3, [ 3,1] f x x x = − + ∈ − 6
1
3028-3031
Find also the local maximum and the local minimum values, as the case may be: (i) f (x) = x2 (ii) g(x) = x3 – 3x (iii) h(x) = sin x + cos x, 0 2 x π < < (iv) f (x) = sin x – cos x, 0 2 <x < π (v) f (x) = x3 – 6x2 + 9x + 15 (vi) 2 ( ) , 0 x2 g x x x = + > (vii) 2 1 ( ) 2 g x x = + (viii) ( ) 1 , 0 1 = − < < f x x x x 4 Prove that the following functions do not have maxima or minima: (i) f (x) = ex (ii) g(x) = log x (iii) h (x) = x3 + x2 + x +1 5 Find the absolute maximum value and the absolute minimum value of the following functions in the given intervals: (i) f (x) = x3, x ∈ [– 2, 2] (ii) f (x) = sin x + cos x , x ∈ [0, π] (iii) f (x) = 12 9 4 , 2, 2 2 x x x   − ∈ −     (iv) 2 ( ) ( 1) 3, [ 3,1] f x x x = − + ∈ − 6 Find the maximum profit that a company can make, if the profit function is given by p(x) = 41 – 72x – 18x2 7
1
3029-3032
Prove that the following functions do not have maxima or minima: (i) f (x) = ex (ii) g(x) = log x (iii) h (x) = x3 + x2 + x +1 5 Find the absolute maximum value and the absolute minimum value of the following functions in the given intervals: (i) f (x) = x3, x ∈ [– 2, 2] (ii) f (x) = sin x + cos x , x ∈ [0, π] (iii) f (x) = 12 9 4 , 2, 2 2 x x x   − ∈ −     (iv) 2 ( ) ( 1) 3, [ 3,1] f x x x = − + ∈ − 6 Find the maximum profit that a company can make, if the profit function is given by p(x) = 41 – 72x – 18x2 7 Find both the maximum value and the minimum value of 3x4 – 8x3 + 12x2 – 48x + 25 on the interval [0, 3]
1
3030-3033
Find the absolute maximum value and the absolute minimum value of the following functions in the given intervals: (i) f (x) = x3, x ∈ [– 2, 2] (ii) f (x) = sin x + cos x , x ∈ [0, π] (iii) f (x) = 12 9 4 , 2, 2 2 x x x   − ∈ −     (iv) 2 ( ) ( 1) 3, [ 3,1] f x x x = − + ∈ − 6 Find the maximum profit that a company can make, if the profit function is given by p(x) = 41 – 72x – 18x2 7 Find both the maximum value and the minimum value of 3x4 – 8x3 + 12x2 – 48x + 25 on the interval [0, 3] 8
1
3031-3034
Find the maximum profit that a company can make, if the profit function is given by p(x) = 41 – 72x – 18x2 7 Find both the maximum value and the minimum value of 3x4 – 8x3 + 12x2 – 48x + 25 on the interval [0, 3] 8 At what points in the interval [0, 2π], does the function sin 2x attain its maximum value
1
3032-3035
Find both the maximum value and the minimum value of 3x4 – 8x3 + 12x2 – 48x + 25 on the interval [0, 3] 8 At what points in the interval [0, 2π], does the function sin 2x attain its maximum value 9
1
3033-3036
8 At what points in the interval [0, 2π], does the function sin 2x attain its maximum value 9 What is the maximum value of the function sin x + cos x
1
3034-3037
At what points in the interval [0, 2π], does the function sin 2x attain its maximum value 9 What is the maximum value of the function sin x + cos x 10
1
3035-3038
9 What is the maximum value of the function sin x + cos x 10 Find the maximum value of 2x3 – 24x + 107 in the interval [1, 3]
1
3036-3039
What is the maximum value of the function sin x + cos x 10 Find the maximum value of 2x3 – 24x + 107 in the interval [1, 3] Find the maximum value of the same function in [–3, –1]
1
3037-3040
10 Find the maximum value of 2x3 – 24x + 107 in the interval [1, 3] Find the maximum value of the same function in [–3, –1] Rationalised 2023-24 MATHEMATICS 176 11
1
3038-3041
Find the maximum value of 2x3 – 24x + 107 in the interval [1, 3] Find the maximum value of the same function in [–3, –1] Rationalised 2023-24 MATHEMATICS 176 11 It is given that at x = 1, the function x4 – 62x2 + ax + 9 attains its maximum value, on the interval [0, 2]
1
3039-3042
Find the maximum value of the same function in [–3, –1] Rationalised 2023-24 MATHEMATICS 176 11 It is given that at x = 1, the function x4 – 62x2 + ax + 9 attains its maximum value, on the interval [0, 2] Find the value of a
1
3040-3043
Rationalised 2023-24 MATHEMATICS 176 11 It is given that at x = 1, the function x4 – 62x2 + ax + 9 attains its maximum value, on the interval [0, 2] Find the value of a 12
1
3041-3044
It is given that at x = 1, the function x4 – 62x2 + ax + 9 attains its maximum value, on the interval [0, 2] Find the value of a 12 Find the maximum and minimum values of x + sin 2x on [0, 2π]
1
3042-3045
Find the value of a 12 Find the maximum and minimum values of x + sin 2x on [0, 2π] 13
1
3043-3046
12 Find the maximum and minimum values of x + sin 2x on [0, 2π] 13 Find two numbers whose sum is 24 and whose product is as large as possible
1
3044-3047
Find the maximum and minimum values of x + sin 2x on [0, 2π] 13 Find two numbers whose sum is 24 and whose product is as large as possible 14
1
3045-3048
13 Find two numbers whose sum is 24 and whose product is as large as possible 14 Find two positive numbers x and y such that x + y = 60 and xy3 is maximum
1
3046-3049
Find two numbers whose sum is 24 and whose product is as large as possible 14 Find two positive numbers x and y such that x + y = 60 and xy3 is maximum 15
1
3047-3050
14 Find two positive numbers x and y such that x + y = 60 and xy3 is maximum 15 Find two positive numbers x and y such that their sum is 35 and the product x2 y5 is a maximum
1
3048-3051
Find two positive numbers x and y such that x + y = 60 and xy3 is maximum 15 Find two positive numbers x and y such that their sum is 35 and the product x2 y5 is a maximum 16
1
3049-3052
15 Find two positive numbers x and y such that their sum is 35 and the product x2 y5 is a maximum 16 Find two positive numbers whose sum is 16 and the sum of whose cubes is minimum
1
3050-3053
Find two positive numbers x and y such that their sum is 35 and the product x2 y5 is a maximum 16 Find two positive numbers whose sum is 16 and the sum of whose cubes is minimum 17
1
3051-3054
16 Find two positive numbers whose sum is 16 and the sum of whose cubes is minimum 17 A square piece of tin of side 18 cm is to be made into a box without top, by cutting a square from each corner and folding up the flaps to form the box
1
3052-3055
Find two positive numbers whose sum is 16 and the sum of whose cubes is minimum 17 A square piece of tin of side 18 cm is to be made into a box without top, by cutting a square from each corner and folding up the flaps to form the box What should be the side of the square to be cut off so that the volume of the box is the maximum possible
1
3053-3056
17 A square piece of tin of side 18 cm is to be made into a box without top, by cutting a square from each corner and folding up the flaps to form the box What should be the side of the square to be cut off so that the volume of the box is the maximum possible 18
1
3054-3057
A square piece of tin of side 18 cm is to be made into a box without top, by cutting a square from each corner and folding up the flaps to form the box What should be the side of the square to be cut off so that the volume of the box is the maximum possible 18 A rectangular sheet of tin 45 cm by 24 cm is to be made into a box without top, by cutting off square from each corner and folding up the flaps
1
3055-3058
What should be the side of the square to be cut off so that the volume of the box is the maximum possible 18 A rectangular sheet of tin 45 cm by 24 cm is to be made into a box without top, by cutting off square from each corner and folding up the flaps What should be the side of the square to be cut off so that the volume of the box is maximum
1
3056-3059
18 A rectangular sheet of tin 45 cm by 24 cm is to be made into a box without top, by cutting off square from each corner and folding up the flaps What should be the side of the square to be cut off so that the volume of the box is maximum 19
1
3057-3060
A rectangular sheet of tin 45 cm by 24 cm is to be made into a box without top, by cutting off square from each corner and folding up the flaps What should be the side of the square to be cut off so that the volume of the box is maximum 19 Show that of all the rectangles inscribed in a given fixed circle, the square has the maximum area
1
3058-3061
What should be the side of the square to be cut off so that the volume of the box is maximum 19 Show that of all the rectangles inscribed in a given fixed circle, the square has the maximum area 20
1
3059-3062
19 Show that of all the rectangles inscribed in a given fixed circle, the square has the maximum area 20 Show that the right circular cylinder of given surface and maximum volume is such that its height is equal to the diameter of the base
1
3060-3063
Show that of all the rectangles inscribed in a given fixed circle, the square has the maximum area 20 Show that the right circular cylinder of given surface and maximum volume is such that its height is equal to the diameter of the base 21
1
3061-3064
20 Show that the right circular cylinder of given surface and maximum volume is such that its height is equal to the diameter of the base 21 Of all the closed cylindrical cans (right circular), of a given volume of 100 cubic centimetres, find the dimensions of the can which has the minimum surface area
1
3062-3065
Show that the right circular cylinder of given surface and maximum volume is such that its height is equal to the diameter of the base 21 Of all the closed cylindrical cans (right circular), of a given volume of 100 cubic centimetres, find the dimensions of the can which has the minimum surface area 22
1
3063-3066
21 Of all the closed cylindrical cans (right circular), of a given volume of 100 cubic centimetres, find the dimensions of the can which has the minimum surface area 22 A wire of length 28 m is to be cut into two pieces
1
3064-3067
Of all the closed cylindrical cans (right circular), of a given volume of 100 cubic centimetres, find the dimensions of the can which has the minimum surface area 22 A wire of length 28 m is to be cut into two pieces One of the pieces is to be made into a square and the other into a circle
1
3065-3068
22 A wire of length 28 m is to be cut into two pieces One of the pieces is to be made into a square and the other into a circle What should be the length of the two pieces so that the combined area of the square and the circle is minimum
1
3066-3069
A wire of length 28 m is to be cut into two pieces One of the pieces is to be made into a square and the other into a circle What should be the length of the two pieces so that the combined area of the square and the circle is minimum 23
1
3067-3070
One of the pieces is to be made into a square and the other into a circle What should be the length of the two pieces so that the combined area of the square and the circle is minimum 23 Prove that the volume of the largest cone that can be inscribed in a sphere of radius R is 8 27 of the volume of the sphere
1
3068-3071
What should be the length of the two pieces so that the combined area of the square and the circle is minimum 23 Prove that the volume of the largest cone that can be inscribed in a sphere of radius R is 8 27 of the volume of the sphere 24
1
3069-3072
23 Prove that the volume of the largest cone that can be inscribed in a sphere of radius R is 8 27 of the volume of the sphere 24 Show that the right circular cone of least curved surface and given volume has an altitude equal to 2 time the radius of the base
1
3070-3073
Prove that the volume of the largest cone that can be inscribed in a sphere of radius R is 8 27 of the volume of the sphere 24 Show that the right circular cone of least curved surface and given volume has an altitude equal to 2 time the radius of the base 25
1
3071-3074
24 Show that the right circular cone of least curved surface and given volume has an altitude equal to 2 time the radius of the base 25 Show that the semi-vertical angle of the cone of the maximum volume and of given slant height is tan1 2 −
1
3072-3075
Show that the right circular cone of least curved surface and given volume has an altitude equal to 2 time the radius of the base 25 Show that the semi-vertical angle of the cone of the maximum volume and of given slant height is tan1 2 − 26
1
3073-3076
25 Show that the semi-vertical angle of the cone of the maximum volume and of given slant height is tan1 2 − 26 Show that semi-vertical angle of right circular cone of given surface area and maximum volume is sin−   1 1 3
1
3074-3077
Show that the semi-vertical angle of the cone of the maximum volume and of given slant height is tan1 2 − 26 Show that semi-vertical angle of right circular cone of given surface area and maximum volume is sin−   1 1 3 Rationalised 2023-24 APPLICATION OF DERIVATIVES 177 Choose the correct answer in Questions 27 and 29
1
3075-3078
26 Show that semi-vertical angle of right circular cone of given surface area and maximum volume is sin−   1 1 3 Rationalised 2023-24 APPLICATION OF DERIVATIVES 177 Choose the correct answer in Questions 27 and 29 27
1
3076-3079
Show that semi-vertical angle of right circular cone of given surface area and maximum volume is sin−   1 1 3 Rationalised 2023-24 APPLICATION OF DERIVATIVES 177 Choose the correct answer in Questions 27 and 29 27 The point on the curve x2 = 2y which is nearest to the point (0, 5) is (A) (2 2,4) (B) (2 2,0) (C) (0, 0) (D) (2, 2) 28
1
3077-3080
Rationalised 2023-24 APPLICATION OF DERIVATIVES 177 Choose the correct answer in Questions 27 and 29 27 The point on the curve x2 = 2y which is nearest to the point (0, 5) is (A) (2 2,4) (B) (2 2,0) (C) (0, 0) (D) (2, 2) 28 For all real values of x, the minimum value of 2 2 1 1 x x x x − + + + is (A) 0 (B) 1 (C) 3 (D) 1 3 29
1
3078-3081
27 The point on the curve x2 = 2y which is nearest to the point (0, 5) is (A) (2 2,4) (B) (2 2,0) (C) (0, 0) (D) (2, 2) 28 For all real values of x, the minimum value of 2 2 1 1 x x x x − + + + is (A) 0 (B) 1 (C) 3 (D) 1 3 29 The maximum value of 31 [ ( 1) 1] x x − + , 0 1 ≤x ≤ is (A) 1 3 31   (B) 1 2 (C) 1 (D) 0 Miscellaneous Examples Example 30 A car starts from a point P at time t = 0 seconds and stops at point Q
1
3079-3082
The point on the curve x2 = 2y which is nearest to the point (0, 5) is (A) (2 2,4) (B) (2 2,0) (C) (0, 0) (D) (2, 2) 28 For all real values of x, the minimum value of 2 2 1 1 x x x x − + + + is (A) 0 (B) 1 (C) 3 (D) 1 3 29 The maximum value of 31 [ ( 1) 1] x x − + , 0 1 ≤x ≤ is (A) 1 3 31   (B) 1 2 (C) 1 (D) 0 Miscellaneous Examples Example 30 A car starts from a point P at time t = 0 seconds and stops at point Q The distance x, in metres, covered by it, in t seconds is given by x t t = −   2 2 3 Find the time taken by it to reach Q and also find distance between P and Q
1
3080-3083
For all real values of x, the minimum value of 2 2 1 1 x x x x − + + + is (A) 0 (B) 1 (C) 3 (D) 1 3 29 The maximum value of 31 [ ( 1) 1] x x − + , 0 1 ≤x ≤ is (A) 1 3 31   (B) 1 2 (C) 1 (D) 0 Miscellaneous Examples Example 30 A car starts from a point P at time t = 0 seconds and stops at point Q The distance x, in metres, covered by it, in t seconds is given by x t t = −   2 2 3 Find the time taken by it to reach Q and also find distance between P and Q Solution Let v be the velocity of the car at t seconds
1
3081-3084
The maximum value of 31 [ ( 1) 1] x x − + , 0 1 ≤x ≤ is (A) 1 3 31   (B) 1 2 (C) 1 (D) 0 Miscellaneous Examples Example 30 A car starts from a point P at time t = 0 seconds and stops at point Q The distance x, in metres, covered by it, in t seconds is given by x t t = −   2 2 3 Find the time taken by it to reach Q and also find distance between P and Q Solution Let v be the velocity of the car at t seconds Now x = 2 2 t3 t   −     Therefore v = dx dt = 4t – t2 = t(4 – t) Thus, v = 0 gives t = 0 and/or t = 4
1
3082-3085
The distance x, in metres, covered by it, in t seconds is given by x t t = −   2 2 3 Find the time taken by it to reach Q and also find distance between P and Q Solution Let v be the velocity of the car at t seconds Now x = 2 2 t3 t   −     Therefore v = dx dt = 4t – t2 = t(4 – t) Thus, v = 0 gives t = 0 and/or t = 4 Now v = 0 at P as well as at Q and at P, t = 0
1
3083-3086
Solution Let v be the velocity of the car at t seconds Now x = 2 2 t3 t   −     Therefore v = dx dt = 4t – t2 = t(4 – t) Thus, v = 0 gives t = 0 and/or t = 4 Now v = 0 at P as well as at Q and at P, t = 0 So, at Q, t = 4
1
3084-3087
Now x = 2 2 t3 t   −     Therefore v = dx dt = 4t – t2 = t(4 – t) Thus, v = 0 gives t = 0 and/or t = 4 Now v = 0 at P as well as at Q and at P, t = 0 So, at Q, t = 4 Thus, the car will reach the point Q after 4 seconds
1
3085-3088
Now v = 0 at P as well as at Q and at P, t = 0 So, at Q, t = 4 Thus, the car will reach the point Q after 4 seconds Also the distance travelled in 4 seconds is given by x]t = 4 = 2 4 2 32 4 2 16 m 3 3 3     − = =         Rationalised 2023-24 MATHEMATICS 178 Example 31 A water tank has the shape of an inverted right circular cone with its axis vertical and vertex lowermost
1
3086-3089
So, at Q, t = 4 Thus, the car will reach the point Q after 4 seconds Also the distance travelled in 4 seconds is given by x]t = 4 = 2 4 2 32 4 2 16 m 3 3 3     − = =         Rationalised 2023-24 MATHEMATICS 178 Example 31 A water tank has the shape of an inverted right circular cone with its axis vertical and vertex lowermost Its semi-vertical angle is tan–1(0
1
3087-3090
Thus, the car will reach the point Q after 4 seconds Also the distance travelled in 4 seconds is given by x]t = 4 = 2 4 2 32 4 2 16 m 3 3 3     − = =         Rationalised 2023-24 MATHEMATICS 178 Example 31 A water tank has the shape of an inverted right circular cone with its axis vertical and vertex lowermost Its semi-vertical angle is tan–1(0 5)
1
3088-3091
Also the distance travelled in 4 seconds is given by x]t = 4 = 2 4 2 32 4 2 16 m 3 3 3     − = =         Rationalised 2023-24 MATHEMATICS 178 Example 31 A water tank has the shape of an inverted right circular cone with its axis vertical and vertex lowermost Its semi-vertical angle is tan–1(0 5) Water is poured into it at a constant rate of 5 cubic metre per hour
1
3089-3092
Its semi-vertical angle is tan–1(0 5) Water is poured into it at a constant rate of 5 cubic metre per hour Find the rate at which the level of the water is rising at the instant when the depth of water in the tank is 4 m
1
3090-3093
5) Water is poured into it at a constant rate of 5 cubic metre per hour Find the rate at which the level of the water is rising at the instant when the depth of water in the tank is 4 m Solution Let r, h and α be as in Fig 6
1
3091-3094
Water is poured into it at a constant rate of 5 cubic metre per hour Find the rate at which the level of the water is rising at the instant when the depth of water in the tank is 4 m Solution Let r, h and α be as in Fig 6 20
1
3092-3095
Find the rate at which the level of the water is rising at the instant when the depth of water in the tank is 4 m Solution Let r, h and α be as in Fig 6 20 Then
1
3093-3096
Solution Let r, h and α be as in Fig 6 20 Then tan hr α = So α = tan1 r h −      
1
3094-3097
20 Then tan hr α = So α = tan1 r h −       But α = tan–1(0
1
3095-3098
Then tan hr α = So α = tan1 r h −       But α = tan–1(0 5) (given) or r h = 0
1
3096-3099
tan hr α = So α = tan1 r h −       But α = tan–1(0 5) (given) or r h = 0 5 or r = 2 h Let V be the volume of the cone
1
3097-3100
But α = tan–1(0 5) (given) or r h = 0 5 or r = 2 h Let V be the volume of the cone Then V = 2 3 2 1 1 3 3 2 12 h h r h h π   π = π =     Therefore dV dt = 3 12 d h dh dh dt   π ⋅     (by Chain Rule) = 2 4 dh h dt π Now rate of change of volume, i
1
3098-3101
5) (given) or r h = 0 5 or r = 2 h Let V be the volume of the cone Then V = 2 3 2 1 1 3 3 2 12 h h r h h π   π = π =     Therefore dV dt = 3 12 d h dh dh dt   π ⋅     (by Chain Rule) = 2 4 dh h dt π Now rate of change of volume, i e
1
3099-3102
5 or r = 2 h Let V be the volume of the cone Then V = 2 3 2 1 1 3 3 2 12 h h r h h π   π = π =     Therefore dV dt = 3 12 d h dh dh dt   π ⋅     (by Chain Rule) = 2 4 dh h dt π Now rate of change of volume, i e , V 5 d dt = m3/h and h = 4 m
1
3100-3103
Then V = 2 3 2 1 1 3 3 2 12 h h r h h π   π = π =     Therefore dV dt = 3 12 d h dh dh dt   π ⋅     (by Chain Rule) = 2 4 dh h dt π Now rate of change of volume, i e , V 5 d dt = m3/h and h = 4 m Therefore 5 = (4)2 4 dh dt π ⋅ or dh dt = 5 35 22 m/h 4 88 7   = π =  π   Thus, the rate of change of water level is 35 m/h 88
1
3101-3104
e , V 5 d dt = m3/h and h = 4 m Therefore 5 = (4)2 4 dh dt π ⋅ or dh dt = 5 35 22 m/h 4 88 7   = π =  π   Thus, the rate of change of water level is 35 m/h 88 Example 32 A man of height 2 metres walks at a uniform speed of 5 km/h away from a lamp post which is 6 metres high
1
3102-3105
, V 5 d dt = m3/h and h = 4 m Therefore 5 = (4)2 4 dh dt π ⋅ or dh dt = 5 35 22 m/h 4 88 7   = π =  π   Thus, the rate of change of water level is 35 m/h 88 Example 32 A man of height 2 metres walks at a uniform speed of 5 km/h away from a lamp post which is 6 metres high Find the rate at which the length of his shadow increases
1
3103-3106
Therefore 5 = (4)2 4 dh dt π ⋅ or dh dt = 5 35 22 m/h 4 88 7   = π =  π   Thus, the rate of change of water level is 35 m/h 88 Example 32 A man of height 2 metres walks at a uniform speed of 5 km/h away from a lamp post which is 6 metres high Find the rate at which the length of his shadow increases Fig 6
1
3104-3107
Example 32 A man of height 2 metres walks at a uniform speed of 5 km/h away from a lamp post which is 6 metres high Find the rate at which the length of his shadow increases Fig 6 20 Rationalised 2023-24 APPLICATION OF DERIVATIVES 179 Solution In Fig 6
1
3105-3108
Find the rate at which the length of his shadow increases Fig 6 20 Rationalised 2023-24 APPLICATION OF DERIVATIVES 179 Solution In Fig 6 21, Let AB be the lamp-post, the lamp being at the position B and let MN be the man at a particular time t and let AM = l metres
1
3106-3109
Fig 6 20 Rationalised 2023-24 APPLICATION OF DERIVATIVES 179 Solution In Fig 6 21, Let AB be the lamp-post, the lamp being at the position B and let MN be the man at a particular time t and let AM = l metres Then, MS is the shadow of the man
1
3107-3110
20 Rationalised 2023-24 APPLICATION OF DERIVATIVES 179 Solution In Fig 6 21, Let AB be the lamp-post, the lamp being at the position B and let MN be the man at a particular time t and let AM = l metres Then, MS is the shadow of the man Let MS = s metres
1
3108-3111
21, Let AB be the lamp-post, the lamp being at the position B and let MN be the man at a particular time t and let AM = l metres Then, MS is the shadow of the man Let MS = s metres Note that ∆MSN ~ ∆ASB or MS AS = MN AB or AS = 3s (as MN = 2 and AB = 6 (given)) Thus AM = 3s – s = 2s
1
3109-3112
Then, MS is the shadow of the man Let MS = s metres Note that ∆MSN ~ ∆ASB or MS AS = MN AB or AS = 3s (as MN = 2 and AB = 6 (given)) Thus AM = 3s – s = 2s But AM = l So l = 2s Therefore dl dt = 2 ds dt Since 5 dl dt = km/h
1
3110-3113
Let MS = s metres Note that ∆MSN ~ ∆ASB or MS AS = MN AB or AS = 3s (as MN = 2 and AB = 6 (given)) Thus AM = 3s – s = 2s But AM = l So l = 2s Therefore dl dt = 2 ds dt Since 5 dl dt = km/h Hence, the length of the shadow increases at the rate 5 2 km/h
1
3111-3114
Note that ∆MSN ~ ∆ASB or MS AS = MN AB or AS = 3s (as MN = 2 and AB = 6 (given)) Thus AM = 3s – s = 2s But AM = l So l = 2s Therefore dl dt = 2 ds dt Since 5 dl dt = km/h Hence, the length of the shadow increases at the rate 5 2 km/h Example 33 Find intervals in which the function given by f (x) = 4 3 2 3 4 36 3 11 10 5 5 x x x x − − + + is (a) increasing (b) decreasing
1
3112-3115
But AM = l So l = 2s Therefore dl dt = 2 ds dt Since 5 dl dt = km/h Hence, the length of the shadow increases at the rate 5 2 km/h Example 33 Find intervals in which the function given by f (x) = 4 3 2 3 4 36 3 11 10 5 5 x x x x − − + + is (a) increasing (b) decreasing Solution We have f (x) = 4 3 2 3 4 36 3 11 10 5 5 x x x x − − + + Therefore f ′(x) = 3 2 3 4 36 (4 ) (3 ) 3(2 ) 10 5 5 x x x − − + = 6( 1)( 2)( 3) 5 x x x − + − (on simplification) Fig 6
1
3113-3116
Hence, the length of the shadow increases at the rate 5 2 km/h Example 33 Find intervals in which the function given by f (x) = 4 3 2 3 4 36 3 11 10 5 5 x x x x − − + + is (a) increasing (b) decreasing Solution We have f (x) = 4 3 2 3 4 36 3 11 10 5 5 x x x x − − + + Therefore f ′(x) = 3 2 3 4 36 (4 ) (3 ) 3(2 ) 10 5 5 x x x − − + = 6( 1)( 2)( 3) 5 x x x − + − (on simplification) Fig 6 21 Rationalised 2023-24 MATHEMATICS 180 Now f ′(x) = 0 gives x = 1, x = – 2, or x = 3
1
3114-3117
Example 33 Find intervals in which the function given by f (x) = 4 3 2 3 4 36 3 11 10 5 5 x x x x − − + + is (a) increasing (b) decreasing Solution We have f (x) = 4 3 2 3 4 36 3 11 10 5 5 x x x x − − + + Therefore f ′(x) = 3 2 3 4 36 (4 ) (3 ) 3(2 ) 10 5 5 x x x − − + = 6( 1)( 2)( 3) 5 x x x − + − (on simplification) Fig 6 21 Rationalised 2023-24 MATHEMATICS 180 Now f ′(x) = 0 gives x = 1, x = – 2, or x = 3 The points x = 1, – 2, and 3 divide the real line into four disjoint intervals namely, (– ∞, – 2), (– 2, 1), (1, 3) and (3, ∞) (Fig 6
1
3115-3118
Solution We have f (x) = 4 3 2 3 4 36 3 11 10 5 5 x x x x − − + + Therefore f ′(x) = 3 2 3 4 36 (4 ) (3 ) 3(2 ) 10 5 5 x x x − − + = 6( 1)( 2)( 3) 5 x x x − + − (on simplification) Fig 6 21 Rationalised 2023-24 MATHEMATICS 180 Now f ′(x) = 0 gives x = 1, x = – 2, or x = 3 The points x = 1, – 2, and 3 divide the real line into four disjoint intervals namely, (– ∞, – 2), (– 2, 1), (1, 3) and (3, ∞) (Fig 6 22)
1
3116-3119
21 Rationalised 2023-24 MATHEMATICS 180 Now f ′(x) = 0 gives x = 1, x = – 2, or x = 3 The points x = 1, – 2, and 3 divide the real line into four disjoint intervals namely, (– ∞, – 2), (– 2, 1), (1, 3) and (3, ∞) (Fig 6 22) Consider the interval (– ∞, – 2), i
1
3117-3120
The points x = 1, – 2, and 3 divide the real line into four disjoint intervals namely, (– ∞, – 2), (– 2, 1), (1, 3) and (3, ∞) (Fig 6 22) Consider the interval (– ∞, – 2), i e