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1 | 3418-3421 | INTEGRALS 299
10 The process of differentiation and integration are inverses of each other as
discussed in Section 7 2 2 (i) |
1 | 3419-3422 | The process of differentiation and integration are inverses of each other as
discussed in Section 7 2 2 (i) EXERCISE 7 |
1 | 3420-3423 | 2 2 (i) EXERCISE 7 1
Find an anti derivative (or integral) of the following functions by the method of inspection |
1 | 3421-3424 | 2 (i) EXERCISE 7 1
Find an anti derivative (or integral) of the following functions by the method of inspection 1 |
1 | 3422-3425 | EXERCISE 7 1
Find an anti derivative (or integral) of the following functions by the method of inspection 1 sin 2x
2 |
1 | 3423-3426 | 1
Find an anti derivative (or integral) of the following functions by the method of inspection 1 sin 2x
2 cos 3x
3 |
1 | 3424-3427 | 1 sin 2x
2 cos 3x
3 e 2x
4 |
1 | 3425-3428 | sin 2x
2 cos 3x
3 e 2x
4 (ax + b)2
5 |
1 | 3426-3429 | cos 3x
3 e 2x
4 (ax + b)2
5 sin 2x – 4 e3x
Find the following integrals in Exercises 6 to 20:
6 |
1 | 3427-3430 | e 2x
4 (ax + b)2
5 sin 2x – 4 e3x
Find the following integrals in Exercises 6 to 20:
6 (4 3
ex+ 1)
dx
∫
7 |
1 | 3428-3431 | (ax + b)2
5 sin 2x – 4 e3x
Find the following integrals in Exercises 6 to 20:
6 (4 3
ex+ 1)
dx
∫
7 2
(1–12
)
x
dx
x
∫
8 |
1 | 3429-3432 | sin 2x – 4 e3x
Find the following integrals in Exercises 6 to 20:
6 (4 3
ex+ 1)
dx
∫
7 2
(1–12
)
x
dx
x
∫
8 2
(
)
ax
bx
c dx
+
+
∫
9 |
1 | 3430-3433 | (4 3
ex+ 1)
dx
∫
7 2
(1–12
)
x
dx
x
∫
8 2
(
)
ax
bx
c dx
+
+
∫
9 (22
x)
x
e
dx
+
∫
10 |
1 | 3431-3434 | 2
(1–12
)
x
dx
x
∫
8 2
(
)
ax
bx
c dx
+
+
∫
9 (22
x)
x
e
dx
+
∫
10 2
x –1
dx
x
∫
11 |
1 | 3432-3435 | 2
(
)
ax
bx
c dx
+
+
∫
9 (22
x)
x
e
dx
+
∫
10 2
x –1
dx
x
∫
11 3
2
2
5
4
x
x –
dx
+x
∫
12 |
1 | 3433-3436 | (22
x)
x
e
dx
+
∫
10 2
x –1
dx
x
∫
11 3
2
2
5
4
x
x –
dx
+x
∫
12 3
3
4
x
x
dx
x
+
+
∫
13 |
1 | 3434-3437 | 2
x –1
dx
x
∫
11 3
2
2
5
4
x
x –
dx
+x
∫
12 3
3
4
x
x
dx
x
+
+
∫
13 3
2
1
1
x
x
x –
dx
−x –
+
∫
14 |
1 | 3435-3438 | 3
2
2
5
4
x
x –
dx
+x
∫
12 3
3
4
x
x
dx
x
+
+
∫
13 3
2
1
1
x
x
x –
dx
−x –
+
∫
14 (1
– x)
x dx
∫
15 |
1 | 3436-3439 | 3
3
4
x
x
dx
x
+
+
∫
13 3
2
1
1
x
x
x –
dx
−x –
+
∫
14 (1
– x)
x dx
∫
15 ( 32
2
3)
x
x
x
dx
+
+
∫
16 |
1 | 3437-3440 | 3
2
1
1
x
x
x –
dx
−x –
+
∫
14 (1
– x)
x dx
∫
15 ( 32
2
3)
x
x
x
dx
+
+
∫
16 (2
3cos
x)
x –
x
e
dx
+
∫
17 |
1 | 3438-3441 | (1
– x)
x dx
∫
15 ( 32
2
3)
x
x
x
dx
+
+
∫
16 (2
3cos
x)
x –
x
e
dx
+
∫
17 (22
3sin
5
)
x –
x
x dx
+
∫
18 |
1 | 3439-3442 | ( 32
2
3)
x
x
x
dx
+
+
∫
16 (2
3cos
x)
x –
x
e
dx
+
∫
17 (22
3sin
5
)
x –
x
x dx
+
∫
18 sec
(sec
tan )
x
x
x dx
+
∫
19 |
1 | 3440-3443 | (2
3cos
x)
x –
x
e
dx
+
∫
17 (22
3sin
5
)
x –
x
x dx
+
∫
18 sec
(sec
tan )
x
x
x dx
+
∫
19 2
sec2
cosec
x
dx
x
∫
20 |
1 | 3441-3444 | (22
3sin
5
)
x –
x
x dx
+
∫
18 sec
(sec
tan )
x
x
x dx
+
∫
19 2
sec2
cosec
x
dx
x
∫
20 2
2 – 3sin
cos
x
x
∫
dx |
1 | 3442-3445 | sec
(sec
tan )
x
x
x dx
+
∫
19 2
sec2
cosec
x
dx
x
∫
20 2
2 – 3sin
cos
x
x
∫
dx Choose the correct answer in Exercises 21 and 22 |
1 | 3443-3446 | 2
sec2
cosec
x
dx
x
∫
20 2
2 – 3sin
cos
x
x
∫
dx Choose the correct answer in Exercises 21 and 22 21 |
1 | 3444-3447 | 2
2 – 3sin
cos
x
x
∫
dx Choose the correct answer in Exercises 21 and 22 21 The anti derivative of
1
x
x
+
equals
(A)
1
1
3
2
1
2
C
3
x
x
+
+
(B)
2
2
23
1
C
3
2
x
x
+
+
(C)
3
1
2
2
2
2
C
3
x
x
+
+
(D)
3
1
2
2
3
1
C
2
2
x
x
+
+
22 |
1 | 3445-3448 | Choose the correct answer in Exercises 21 and 22 21 The anti derivative of
1
x
x
+
equals
(A)
1
1
3
2
1
2
C
3
x
x
+
+
(B)
2
2
23
1
C
3
2
x
x
+
+
(C)
3
1
2
2
2
2
C
3
x
x
+
+
(D)
3
1
2
2
3
1
C
2
2
x
x
+
+
22 If
3
34
( )
4
d f x
x
dx
x
=
−
such that f (2) = 0 |
1 | 3446-3449 | 21 The anti derivative of
1
x
x
+
equals
(A)
1
1
3
2
1
2
C
3
x
x
+
+
(B)
2
2
23
1
C
3
2
x
x
+
+
(C)
3
1
2
2
2
2
C
3
x
x
+
+
(D)
3
1
2
2
3
1
C
2
2
x
x
+
+
22 If
3
34
( )
4
d f x
x
dx
x
=
−
such that f (2) = 0 Then f (x) is
(A)
4
13
129
8
x
+x
−
(B)
3
14
129
8
x
+x
+
(C)
4
13
129
8
x
+x
+
(D)
3
14
129
8
x
+x
−
300
MATHEMATICS
7 |
1 | 3447-3450 | The anti derivative of
1
x
x
+
equals
(A)
1
1
3
2
1
2
C
3
x
x
+
+
(B)
2
2
23
1
C
3
2
x
x
+
+
(C)
3
1
2
2
2
2
C
3
x
x
+
+
(D)
3
1
2
2
3
1
C
2
2
x
x
+
+
22 If
3
34
( )
4
d f x
x
dx
x
=
−
such that f (2) = 0 Then f (x) is
(A)
4
13
129
8
x
+x
−
(B)
3
14
129
8
x
+x
+
(C)
4
13
129
8
x
+x
+
(D)
3
14
129
8
x
+x
−
300
MATHEMATICS
7 3 Methods of Integration
In previous section, we discussed integrals of those functions which were readily
obtainable from derivatives of some functions |
1 | 3448-3451 | If
3
34
( )
4
d f x
x
dx
x
=
−
such that f (2) = 0 Then f (x) is
(A)
4
13
129
8
x
+x
−
(B)
3
14
129
8
x
+x
+
(C)
4
13
129
8
x
+x
+
(D)
3
14
129
8
x
+x
−
300
MATHEMATICS
7 3 Methods of Integration
In previous section, we discussed integrals of those functions which were readily
obtainable from derivatives of some functions It was based on inspection, i |
1 | 3449-3452 | Then f (x) is
(A)
4
13
129
8
x
+x
−
(B)
3
14
129
8
x
+x
+
(C)
4
13
129
8
x
+x
+
(D)
3
14
129
8
x
+x
−
300
MATHEMATICS
7 3 Methods of Integration
In previous section, we discussed integrals of those functions which were readily
obtainable from derivatives of some functions It was based on inspection, i e |
1 | 3450-3453 | 3 Methods of Integration
In previous section, we discussed integrals of those functions which were readily
obtainable from derivatives of some functions It was based on inspection, i e , on the
search of a function F whose derivative is f which led us to the integral of f |
1 | 3451-3454 | It was based on inspection, i e , on the
search of a function F whose derivative is f which led us to the integral of f However,
this method, which depends on inspection, is not very suitable for many functions |
1 | 3452-3455 | e , on the
search of a function F whose derivative is f which led us to the integral of f However,
this method, which depends on inspection, is not very suitable for many functions Hence, we need to develop additional techniques or methods for finding the integrals
by reducing them into standard forms |
1 | 3453-3456 | , on the
search of a function F whose derivative is f which led us to the integral of f However,
this method, which depends on inspection, is not very suitable for many functions Hence, we need to develop additional techniques or methods for finding the integrals
by reducing them into standard forms Prominent among them are methods based on:
1 |
1 | 3454-3457 | However,
this method, which depends on inspection, is not very suitable for many functions Hence, we need to develop additional techniques or methods for finding the integrals
by reducing them into standard forms Prominent among them are methods based on:
1 Integration by Substitution
2 |
1 | 3455-3458 | Hence, we need to develop additional techniques or methods for finding the integrals
by reducing them into standard forms Prominent among them are methods based on:
1 Integration by Substitution
2 Integration using Partial Fractions
3 |
1 | 3456-3459 | Prominent among them are methods based on:
1 Integration by Substitution
2 Integration using Partial Fractions
3 Integration by Parts
7 |
1 | 3457-3460 | Integration by Substitution
2 Integration using Partial Fractions
3 Integration by Parts
7 3 |
1 | 3458-3461 | Integration using Partial Fractions
3 Integration by Parts
7 3 1 Integration by substitution
In this section, we consider the method of integration by substitution |
1 | 3459-3462 | Integration by Parts
7 3 1 Integration by substitution
In this section, we consider the method of integration by substitution The given integral
( )
∫f x dx
can be transformed into another form by changing
the independent variable x to t by substituting x = g (t) |
1 | 3460-3463 | 3 1 Integration by substitution
In this section, we consider the method of integration by substitution The given integral
( )
∫f x dx
can be transformed into another form by changing
the independent variable x to t by substituting x = g (t) Consider
I =
( )
f x dx
∫
Put x = g(t) so that dx
dt = g′(t) |
1 | 3461-3464 | 1 Integration by substitution
In this section, we consider the method of integration by substitution The given integral
( )
∫f x dx
can be transformed into another form by changing
the independent variable x to t by substituting x = g (t) Consider
I =
( )
f x dx
∫
Put x = g(t) so that dx
dt = g′(t) We write
dx = g′(t) dt
Thus
I =
( )
( ( ))
( )
f x dx
f g t
g t dt
=
′
∫
∫
This change of variable formula is one of the important tools available to us in the
name of integration by substitution |
1 | 3462-3465 | The given integral
( )
∫f x dx
can be transformed into another form by changing
the independent variable x to t by substituting x = g (t) Consider
I =
( )
f x dx
∫
Put x = g(t) so that dx
dt = g′(t) We write
dx = g′(t) dt
Thus
I =
( )
( ( ))
( )
f x dx
f g t
g t dt
=
′
∫
∫
This change of variable formula is one of the important tools available to us in the
name of integration by substitution It is often important to guess what will be the useful
substitution |
1 | 3463-3466 | Consider
I =
( )
f x dx
∫
Put x = g(t) so that dx
dt = g′(t) We write
dx = g′(t) dt
Thus
I =
( )
( ( ))
( )
f x dx
f g t
g t dt
=
′
∫
∫
This change of variable formula is one of the important tools available to us in the
name of integration by substitution It is often important to guess what will be the useful
substitution Usually, we make a substitution for a function whose derivative also occurs
in the integrand as illustrated in the following examples |
1 | 3464-3467 | We write
dx = g′(t) dt
Thus
I =
( )
( ( ))
( )
f x dx
f g t
g t dt
=
′
∫
∫
This change of variable formula is one of the important tools available to us in the
name of integration by substitution It is often important to guess what will be the useful
substitution Usually, we make a substitution for a function whose derivative also occurs
in the integrand as illustrated in the following examples Example 5 Integrate the following functions w |
1 | 3465-3468 | It is often important to guess what will be the useful
substitution Usually, we make a substitution for a function whose derivative also occurs
in the integrand as illustrated in the following examples Example 5 Integrate the following functions w r |
1 | 3466-3469 | Usually, we make a substitution for a function whose derivative also occurs
in the integrand as illustrated in the following examples Example 5 Integrate the following functions w r t |
1 | 3467-3470 | Example 5 Integrate the following functions w r t x:
(i)
sin mx
(ii)
2x sin (x2 + 1)
(iii)
4
2
tan
xsec
x
x
(iv)
1
2
sin (tan
)
1
x– x
+
Solution
(i)
We know that derivative of mx is m |
1 | 3468-3471 | r t x:
(i)
sin mx
(ii)
2x sin (x2 + 1)
(iii)
4
2
tan
xsec
x
x
(iv)
1
2
sin (tan
)
1
x– x
+
Solution
(i)
We know that derivative of mx is m Thus, we make the substitution
mx = t so that mdx = dt |
1 | 3469-3472 | t x:
(i)
sin mx
(ii)
2x sin (x2 + 1)
(iii)
4
2
tan
xsec
x
x
(iv)
1
2
sin (tan
)
1
x– x
+
Solution
(i)
We know that derivative of mx is m Thus, we make the substitution
mx = t so that mdx = dt Therefore,
1
sin
sin
mx dx
t dt
m
=
∫
∫
= – 1
m
cos t + C = – 1
m cos mx + C
INTEGRALS 301
(ii)
Derivative of x2 + 1 is 2x |
1 | 3470-3473 | x:
(i)
sin mx
(ii)
2x sin (x2 + 1)
(iii)
4
2
tan
xsec
x
x
(iv)
1
2
sin (tan
)
1
x– x
+
Solution
(i)
We know that derivative of mx is m Thus, we make the substitution
mx = t so that mdx = dt Therefore,
1
sin
sin
mx dx
t dt
m
=
∫
∫
= – 1
m
cos t + C = – 1
m cos mx + C
INTEGRALS 301
(ii)
Derivative of x2 + 1 is 2x Thus, we use the substitution x2 + 1 = t so that
2x dx = dt |
1 | 3471-3474 | Thus, we make the substitution
mx = t so that mdx = dt Therefore,
1
sin
sin
mx dx
t dt
m
=
∫
∫
= – 1
m
cos t + C = – 1
m cos mx + C
INTEGRALS 301
(ii)
Derivative of x2 + 1 is 2x Thus, we use the substitution x2 + 1 = t so that
2x dx = dt Therefore,
2 sin (2
1)
sin
x
x
dx
t dt
+
=
∫
∫
= – cos t + C = – cos (x2 + 1) + C
(iii)
Derivative of
x is
21
1
1
2
2
–
x
x
= |
1 | 3472-3475 | Therefore,
1
sin
sin
mx dx
t dt
m
=
∫
∫
= – 1
m
cos t + C = – 1
m cos mx + C
INTEGRALS 301
(ii)
Derivative of x2 + 1 is 2x Thus, we use the substitution x2 + 1 = t so that
2x dx = dt Therefore,
2 sin (2
1)
sin
x
x
dx
t dt
+
=
∫
∫
= – cos t + C = – cos (x2 + 1) + C
(iii)
Derivative of
x is
21
1
1
2
2
–
x
x
= Thus, we use the substitution
1
so that
giving
2
x
t
dx
dt
x
=
=
dx = 2t dt |
1 | 3473-3476 | Thus, we use the substitution x2 + 1 = t so that
2x dx = dt Therefore,
2 sin (2
1)
sin
x
x
dx
t dt
+
=
∫
∫
= – cos t + C = – cos (x2 + 1) + C
(iii)
Derivative of
x is
21
1
1
2
2
–
x
x
= Thus, we use the substitution
1
so that
giving
2
x
t
dx
dt
x
=
=
dx = 2t dt Thus,
4
2
4
2
tan
sec
2 tan
sec
x
x
t
t
t dt
dx
t
x
=
∫
∫
=
4
2
2 tan
tsec
t dt
∫
Again, we make another substitution tan t = u so that
sec2 t dt = du
Therefore,
4
2
4
2 tan
sec
2
t
t dt
u du
=
∫
∫
=
5
2
C
5
u +
=
2 tan5
C
5
t +
(since u = tan t)
=
2 tan5
C (since
)
5
x
t
x
+
=
Hence,
4
2
tan
xsec
x dx
x
∫
=
2 tan5
C
5
x +
Alternatively, make the substitution tan
x
t
=
(iv)
Derivative of
1
2
1
tan
1
– x
x
= + |
1 | 3474-3477 | Therefore,
2 sin (2
1)
sin
x
x
dx
t dt
+
=
∫
∫
= – cos t + C = – cos (x2 + 1) + C
(iii)
Derivative of
x is
21
1
1
2
2
–
x
x
= Thus, we use the substitution
1
so that
giving
2
x
t
dx
dt
x
=
=
dx = 2t dt Thus,
4
2
4
2
tan
sec
2 tan
sec
x
x
t
t
t dt
dx
t
x
=
∫
∫
=
4
2
2 tan
tsec
t dt
∫
Again, we make another substitution tan t = u so that
sec2 t dt = du
Therefore,
4
2
4
2 tan
sec
2
t
t dt
u du
=
∫
∫
=
5
2
C
5
u +
=
2 tan5
C
5
t +
(since u = tan t)
=
2 tan5
C (since
)
5
x
t
x
+
=
Hence,
4
2
tan
xsec
x dx
x
∫
=
2 tan5
C
5
x +
Alternatively, make the substitution tan
x
t
=
(iv)
Derivative of
1
2
1
tan
1
– x
x
= + Thus, we use the substitution
tan–1 x = t so that
2
1
dx
x
+
= dt |
1 | 3475-3478 | Thus, we use the substitution
1
so that
giving
2
x
t
dx
dt
x
=
=
dx = 2t dt Thus,
4
2
4
2
tan
sec
2 tan
sec
x
x
t
t
t dt
dx
t
x
=
∫
∫
=
4
2
2 tan
tsec
t dt
∫
Again, we make another substitution tan t = u so that
sec2 t dt = du
Therefore,
4
2
4
2 tan
sec
2
t
t dt
u du
=
∫
∫
=
5
2
C
5
u +
=
2 tan5
C
5
t +
(since u = tan t)
=
2 tan5
C (since
)
5
x
t
x
+
=
Hence,
4
2
tan
xsec
x dx
x
∫
=
2 tan5
C
5
x +
Alternatively, make the substitution tan
x
t
=
(iv)
Derivative of
1
2
1
tan
1
– x
x
= + Thus, we use the substitution
tan–1 x = t so that
2
1
dx
x
+
= dt Therefore ,
1
sin (tan2
)
sin
1
– x dx
t dt
x
=
+
∫
∫
= – cos t + C = – cos (tan –1x) + C
Now, we discuss some important integrals involving trigonometric functions and
their standard integrals using substitution technique |
1 | 3476-3479 | Thus,
4
2
4
2
tan
sec
2 tan
sec
x
x
t
t
t dt
dx
t
x
=
∫
∫
=
4
2
2 tan
tsec
t dt
∫
Again, we make another substitution tan t = u so that
sec2 t dt = du
Therefore,
4
2
4
2 tan
sec
2
t
t dt
u du
=
∫
∫
=
5
2
C
5
u +
=
2 tan5
C
5
t +
(since u = tan t)
=
2 tan5
C (since
)
5
x
t
x
+
=
Hence,
4
2
tan
xsec
x dx
x
∫
=
2 tan5
C
5
x +
Alternatively, make the substitution tan
x
t
=
(iv)
Derivative of
1
2
1
tan
1
– x
x
= + Thus, we use the substitution
tan–1 x = t so that
2
1
dx
x
+
= dt Therefore ,
1
sin (tan2
)
sin
1
– x dx
t dt
x
=
+
∫
∫
= – cos t + C = – cos (tan –1x) + C
Now, we discuss some important integrals involving trigonometric functions and
their standard integrals using substitution technique These will be used later without
reference |
1 | 3477-3480 | Thus, we use the substitution
tan–1 x = t so that
2
1
dx
x
+
= dt Therefore ,
1
sin (tan2
)
sin
1
– x dx
t dt
x
=
+
∫
∫
= – cos t + C = – cos (tan –1x) + C
Now, we discuss some important integrals involving trigonometric functions and
their standard integrals using substitution technique These will be used later without
reference (i) ∫tan
= log sec
+ C
x dx
x
We have
sin
tan
cos
x
x dx
dx
x
=
∫
∫
302
MATHEMATICS
Put cos x = t so that sin x dx = – dt
Then
tan
log
C
log cos
C
dt
x dx
–
–
t
–
x
t
=
=
+
=
+
∫
∫
or
tan
log sec
C
x dx
x
=
+
∫
(ii) ∫cot
= log sin
+ C
x dx
x
We have
cos
cot
sin
x
x dx
dx
x
=
∫
∫
Put sin x = t so that cos x dx = dt
Then
cot
dt
x dx
t
=
∫
∫
= log
t +C
= log sin
C
x +
(iii) ∫sec
= log sec
+ tan
+ C
x dx
x
x
We have
sec
(sec
tan )
sec
sec
+ tan
x
x
x
x dx
dx
x
+x
=
∫
∫
Put sec x + tan x = t so that sec x (tan x + sec x) dx = dt
Therefore, sec
log
+ C = log sec
tan
C
dt
x dx
t
x
x
t
=
=
+
+
∫
∫
(iv) ∫cosec
= log cosec
– cot
+ C
x dx
x
x
We have
cosec
(cosec
cot )
cosec
(cosec
cot )
x
x
x
x dx
dx
x
+x
=
+
∫
∫
Put cosec x + cot x = t so that – cosec x (cosec x + cot x) dx = dt
So
cosec
–
–log| |
– log|cosec
cot
|
C
dt
x dx
t
x
x
t
=
=
=
+
+
∫
∫
=
2
2
cosec
cot
– log
C
cosec
cot
x
x
x
x
−
+
−
= log cosec
cot
C
x –
x +
Example 6 Find the following integrals:
(i)
3
2
sin
xcos
x dx
∫
(ii)
sin
sin (
)
x
dx
x
+a
∫
(iii)
1
1
tan
dx
x
∫+
INTEGRALS 303
Solution
(i)
We have
3
2
2
2
sin
cos
sin
cos
(sin )
x
x dx
x
x
x dx
=
∫
∫
=
2
2
(1– cos
) cos
(sin )
x
x
x dx
∫
Put t = cos x so that dt = – sin x dx
Therefore,
2
2
sin
cos
(sin )
x
x
x dx
∫
=
2
2
(1–
t)
t dt
−∫
=
3
5
2
4
(
–
)
C
3
5
t
t
–
t
t
dt
–
–
=
+
∫
=
3
5
1
1
cos
cos
C
3
5
–
x
x
+
+
(ii)
Put x + a = t |
1 | 3478-3481 | Therefore ,
1
sin (tan2
)
sin
1
– x dx
t dt
x
=
+
∫
∫
= – cos t + C = – cos (tan –1x) + C
Now, we discuss some important integrals involving trigonometric functions and
their standard integrals using substitution technique These will be used later without
reference (i) ∫tan
= log sec
+ C
x dx
x
We have
sin
tan
cos
x
x dx
dx
x
=
∫
∫
302
MATHEMATICS
Put cos x = t so that sin x dx = – dt
Then
tan
log
C
log cos
C
dt
x dx
–
–
t
–
x
t
=
=
+
=
+
∫
∫
or
tan
log sec
C
x dx
x
=
+
∫
(ii) ∫cot
= log sin
+ C
x dx
x
We have
cos
cot
sin
x
x dx
dx
x
=
∫
∫
Put sin x = t so that cos x dx = dt
Then
cot
dt
x dx
t
=
∫
∫
= log
t +C
= log sin
C
x +
(iii) ∫sec
= log sec
+ tan
+ C
x dx
x
x
We have
sec
(sec
tan )
sec
sec
+ tan
x
x
x
x dx
dx
x
+x
=
∫
∫
Put sec x + tan x = t so that sec x (tan x + sec x) dx = dt
Therefore, sec
log
+ C = log sec
tan
C
dt
x dx
t
x
x
t
=
=
+
+
∫
∫
(iv) ∫cosec
= log cosec
– cot
+ C
x dx
x
x
We have
cosec
(cosec
cot )
cosec
(cosec
cot )
x
x
x
x dx
dx
x
+x
=
+
∫
∫
Put cosec x + cot x = t so that – cosec x (cosec x + cot x) dx = dt
So
cosec
–
–log| |
– log|cosec
cot
|
C
dt
x dx
t
x
x
t
=
=
=
+
+
∫
∫
=
2
2
cosec
cot
– log
C
cosec
cot
x
x
x
x
−
+
−
= log cosec
cot
C
x –
x +
Example 6 Find the following integrals:
(i)
3
2
sin
xcos
x dx
∫
(ii)
sin
sin (
)
x
dx
x
+a
∫
(iii)
1
1
tan
dx
x
∫+
INTEGRALS 303
Solution
(i)
We have
3
2
2
2
sin
cos
sin
cos
(sin )
x
x dx
x
x
x dx
=
∫
∫
=
2
2
(1– cos
) cos
(sin )
x
x
x dx
∫
Put t = cos x so that dt = – sin x dx
Therefore,
2
2
sin
cos
(sin )
x
x
x dx
∫
=
2
2
(1–
t)
t dt
−∫
=
3
5
2
4
(
–
)
C
3
5
t
t
–
t
t
dt
–
–
=
+
∫
=
3
5
1
1
cos
cos
C
3
5
–
x
x
+
+
(ii)
Put x + a = t Then dx = dt |
1 | 3479-3482 | These will be used later without
reference (i) ∫tan
= log sec
+ C
x dx
x
We have
sin
tan
cos
x
x dx
dx
x
=
∫
∫
302
MATHEMATICS
Put cos x = t so that sin x dx = – dt
Then
tan
log
C
log cos
C
dt
x dx
–
–
t
–
x
t
=
=
+
=
+
∫
∫
or
tan
log sec
C
x dx
x
=
+
∫
(ii) ∫cot
= log sin
+ C
x dx
x
We have
cos
cot
sin
x
x dx
dx
x
=
∫
∫
Put sin x = t so that cos x dx = dt
Then
cot
dt
x dx
t
=
∫
∫
= log
t +C
= log sin
C
x +
(iii) ∫sec
= log sec
+ tan
+ C
x dx
x
x
We have
sec
(sec
tan )
sec
sec
+ tan
x
x
x
x dx
dx
x
+x
=
∫
∫
Put sec x + tan x = t so that sec x (tan x + sec x) dx = dt
Therefore, sec
log
+ C = log sec
tan
C
dt
x dx
t
x
x
t
=
=
+
+
∫
∫
(iv) ∫cosec
= log cosec
– cot
+ C
x dx
x
x
We have
cosec
(cosec
cot )
cosec
(cosec
cot )
x
x
x
x dx
dx
x
+x
=
+
∫
∫
Put cosec x + cot x = t so that – cosec x (cosec x + cot x) dx = dt
So
cosec
–
–log| |
– log|cosec
cot
|
C
dt
x dx
t
x
x
t
=
=
=
+
+
∫
∫
=
2
2
cosec
cot
– log
C
cosec
cot
x
x
x
x
−
+
−
= log cosec
cot
C
x –
x +
Example 6 Find the following integrals:
(i)
3
2
sin
xcos
x dx
∫
(ii)
sin
sin (
)
x
dx
x
+a
∫
(iii)
1
1
tan
dx
x
∫+
INTEGRALS 303
Solution
(i)
We have
3
2
2
2
sin
cos
sin
cos
(sin )
x
x dx
x
x
x dx
=
∫
∫
=
2
2
(1– cos
) cos
(sin )
x
x
x dx
∫
Put t = cos x so that dt = – sin x dx
Therefore,
2
2
sin
cos
(sin )
x
x
x dx
∫
=
2
2
(1–
t)
t dt
−∫
=
3
5
2
4
(
–
)
C
3
5
t
t
–
t
t
dt
–
–
=
+
∫
=
3
5
1
1
cos
cos
C
3
5
–
x
x
+
+
(ii)
Put x + a = t Then dx = dt Therefore
sin
sin (
)
sin (
)
sin
x
t – a
dx
dt
x
a
t
=
+
∫
∫
=
sin cos
cos sin
sin
t
a –
t
a dt
t
∫
= cos
– sin
cot
a dt
a
t dt
∫
∫
=
1
(cos )
(sin ) log sin
C
a t –
a
t
+
=
1
(cos ) (
)
(sin ) log sin (
)
C
a
x
a –
a
x
a
+
+
+
=
1
cos
cos
(sin ) log sin (
)
C sin
x
a
a
a –
a
x
a –
a
+
+
Hence,
sin
sin (
)
x
dx
x
+a
∫
= x cos a – sin a log |sin (x + a)| + C,
where, C = – C1 sin a + a cos a, is another arbitrary constant |
1 | 3480-3483 | (i) ∫tan
= log sec
+ C
x dx
x
We have
sin
tan
cos
x
x dx
dx
x
=
∫
∫
302
MATHEMATICS
Put cos x = t so that sin x dx = – dt
Then
tan
log
C
log cos
C
dt
x dx
–
–
t
–
x
t
=
=
+
=
+
∫
∫
or
tan
log sec
C
x dx
x
=
+
∫
(ii) ∫cot
= log sin
+ C
x dx
x
We have
cos
cot
sin
x
x dx
dx
x
=
∫
∫
Put sin x = t so that cos x dx = dt
Then
cot
dt
x dx
t
=
∫
∫
= log
t +C
= log sin
C
x +
(iii) ∫sec
= log sec
+ tan
+ C
x dx
x
x
We have
sec
(sec
tan )
sec
sec
+ tan
x
x
x
x dx
dx
x
+x
=
∫
∫
Put sec x + tan x = t so that sec x (tan x + sec x) dx = dt
Therefore, sec
log
+ C = log sec
tan
C
dt
x dx
t
x
x
t
=
=
+
+
∫
∫
(iv) ∫cosec
= log cosec
– cot
+ C
x dx
x
x
We have
cosec
(cosec
cot )
cosec
(cosec
cot )
x
x
x
x dx
dx
x
+x
=
+
∫
∫
Put cosec x + cot x = t so that – cosec x (cosec x + cot x) dx = dt
So
cosec
–
–log| |
– log|cosec
cot
|
C
dt
x dx
t
x
x
t
=
=
=
+
+
∫
∫
=
2
2
cosec
cot
– log
C
cosec
cot
x
x
x
x
−
+
−
= log cosec
cot
C
x –
x +
Example 6 Find the following integrals:
(i)
3
2
sin
xcos
x dx
∫
(ii)
sin
sin (
)
x
dx
x
+a
∫
(iii)
1
1
tan
dx
x
∫+
INTEGRALS 303
Solution
(i)
We have
3
2
2
2
sin
cos
sin
cos
(sin )
x
x dx
x
x
x dx
=
∫
∫
=
2
2
(1– cos
) cos
(sin )
x
x
x dx
∫
Put t = cos x so that dt = – sin x dx
Therefore,
2
2
sin
cos
(sin )
x
x
x dx
∫
=
2
2
(1–
t)
t dt
−∫
=
3
5
2
4
(
–
)
C
3
5
t
t
–
t
t
dt
–
–
=
+
∫
=
3
5
1
1
cos
cos
C
3
5
–
x
x
+
+
(ii)
Put x + a = t Then dx = dt Therefore
sin
sin (
)
sin (
)
sin
x
t – a
dx
dt
x
a
t
=
+
∫
∫
=
sin cos
cos sin
sin
t
a –
t
a dt
t
∫
= cos
– sin
cot
a dt
a
t dt
∫
∫
=
1
(cos )
(sin ) log sin
C
a t –
a
t
+
=
1
(cos ) (
)
(sin ) log sin (
)
C
a
x
a –
a
x
a
+
+
+
=
1
cos
cos
(sin ) log sin (
)
C sin
x
a
a
a –
a
x
a –
a
+
+
Hence,
sin
sin (
)
x
dx
x
+a
∫
= x cos a – sin a log |sin (x + a)| + C,
where, C = – C1 sin a + a cos a, is another arbitrary constant (iii)
cos
1
tan
cos
sin
dx
x dx
x
x
x
=
+
+
∫
∫
=
1
(cos
+ sin
+ cos
– sin )
2
cos
sin
x
x
x
x dx
x
x
+
∫
304
MATHEMATICS
=
1
1
cos
– sin
2
2
cos
sin
x
x
dx
dx
x
x
+
+
∫
∫
=
C1
1
cos
sin
2
2
2
cos
sin
x
x –
x dx
x
x
+
+
+
∫ |
1 | 3481-3484 | Then dx = dt Therefore
sin
sin (
)
sin (
)
sin
x
t – a
dx
dt
x
a
t
=
+
∫
∫
=
sin cos
cos sin
sin
t
a –
t
a dt
t
∫
= cos
– sin
cot
a dt
a
t dt
∫
∫
=
1
(cos )
(sin ) log sin
C
a t –
a
t
+
=
1
(cos ) (
)
(sin ) log sin (
)
C
a
x
a –
a
x
a
+
+
+
=
1
cos
cos
(sin ) log sin (
)
C sin
x
a
a
a –
a
x
a –
a
+
+
Hence,
sin
sin (
)
x
dx
x
+a
∫
= x cos a – sin a log |sin (x + a)| + C,
where, C = – C1 sin a + a cos a, is another arbitrary constant (iii)
cos
1
tan
cos
sin
dx
x dx
x
x
x
=
+
+
∫
∫
=
1
(cos
+ sin
+ cos
– sin )
2
cos
sin
x
x
x
x dx
x
x
+
∫
304
MATHEMATICS
=
1
1
cos
– sin
2
2
cos
sin
x
x
dx
dx
x
x
+
+
∫
∫
=
C1
1
cos
sin
2
2
2
cos
sin
x
x –
x dx
x
x
+
+
+
∫ (1)
Now, consider
cos
sin
I
cos
sin
x –
x dx
x
x
=
+
∫
Put cos x + sin x = t so that (cos x – sin x) dx = dt
Therefore
2
I
log
C
dt
t
t
=
=
+
∫
=
2
log cos
sin
C
x
x
+
+
Putting it in (1), we get
1
2
C
C
1
+
+
log cos
sin
1
tan
2
2
2
2
dx
x
x
x
x
=
+
+
+
∫
=
1
2
C
C
+1
log cos
sin
2
2
2
2
x
x
x
+
+
+
=
1
2
C
C
+1
log cos
sin
C
C
2
2
2
2
x
x
x
,
+
+
=
+
EXERCISE 7 |
1 | 3482-3485 | Therefore
sin
sin (
)
sin (
)
sin
x
t – a
dx
dt
x
a
t
=
+
∫
∫
=
sin cos
cos sin
sin
t
a –
t
a dt
t
∫
= cos
– sin
cot
a dt
a
t dt
∫
∫
=
1
(cos )
(sin ) log sin
C
a t –
a
t
+
=
1
(cos ) (
)
(sin ) log sin (
)
C
a
x
a –
a
x
a
+
+
+
=
1
cos
cos
(sin ) log sin (
)
C sin
x
a
a
a –
a
x
a –
a
+
+
Hence,
sin
sin (
)
x
dx
x
+a
∫
= x cos a – sin a log |sin (x + a)| + C,
where, C = – C1 sin a + a cos a, is another arbitrary constant (iii)
cos
1
tan
cos
sin
dx
x dx
x
x
x
=
+
+
∫
∫
=
1
(cos
+ sin
+ cos
– sin )
2
cos
sin
x
x
x
x dx
x
x
+
∫
304
MATHEMATICS
=
1
1
cos
– sin
2
2
cos
sin
x
x
dx
dx
x
x
+
+
∫
∫
=
C1
1
cos
sin
2
2
2
cos
sin
x
x –
x dx
x
x
+
+
+
∫ (1)
Now, consider
cos
sin
I
cos
sin
x –
x dx
x
x
=
+
∫
Put cos x + sin x = t so that (cos x – sin x) dx = dt
Therefore
2
I
log
C
dt
t
t
=
=
+
∫
=
2
log cos
sin
C
x
x
+
+
Putting it in (1), we get
1
2
C
C
1
+
+
log cos
sin
1
tan
2
2
2
2
dx
x
x
x
x
=
+
+
+
∫
=
1
2
C
C
+1
log cos
sin
2
2
2
2
x
x
x
+
+
+
=
1
2
C
C
+1
log cos
sin
C
C
2
2
2
2
x
x
x
,
+
+
=
+
EXERCISE 7 2
Integrate the functions in Exercises 1 to 37:
1 |
1 | 3483-3486 | (iii)
cos
1
tan
cos
sin
dx
x dx
x
x
x
=
+
+
∫
∫
=
1
(cos
+ sin
+ cos
– sin )
2
cos
sin
x
x
x
x dx
x
x
+
∫
304
MATHEMATICS
=
1
1
cos
– sin
2
2
cos
sin
x
x
dx
dx
x
x
+
+
∫
∫
=
C1
1
cos
sin
2
2
2
cos
sin
x
x –
x dx
x
x
+
+
+
∫ (1)
Now, consider
cos
sin
I
cos
sin
x –
x dx
x
x
=
+
∫
Put cos x + sin x = t so that (cos x – sin x) dx = dt
Therefore
2
I
log
C
dt
t
t
=
=
+
∫
=
2
log cos
sin
C
x
x
+
+
Putting it in (1), we get
1
2
C
C
1
+
+
log cos
sin
1
tan
2
2
2
2
dx
x
x
x
x
=
+
+
+
∫
=
1
2
C
C
+1
log cos
sin
2
2
2
2
x
x
x
+
+
+
=
1
2
C
C
+1
log cos
sin
C
C
2
2
2
2
x
x
x
,
+
+
=
+
EXERCISE 7 2
Integrate the functions in Exercises 1 to 37:
1 2
2
1
+xx
2 |
1 | 3484-3487 | (1)
Now, consider
cos
sin
I
cos
sin
x –
x dx
x
x
=
+
∫
Put cos x + sin x = t so that (cos x – sin x) dx = dt
Therefore
2
I
log
C
dt
t
t
=
=
+
∫
=
2
log cos
sin
C
x
x
+
+
Putting it in (1), we get
1
2
C
C
1
+
+
log cos
sin
1
tan
2
2
2
2
dx
x
x
x
x
=
+
+
+
∫
=
1
2
C
C
+1
log cos
sin
2
2
2
2
x
x
x
+
+
+
=
1
2
C
C
+1
log cos
sin
C
C
2
2
2
2
x
x
x
,
+
+
=
+
EXERCISE 7 2
Integrate the functions in Exercises 1 to 37:
1 2
2
1
+xx
2 (
)
2
log x
x
3 |
1 | 3485-3488 | 2
Integrate the functions in Exercises 1 to 37:
1 2
2
1
+xx
2 (
)
2
log x
x
3 1
log
x
x
x
+
4 |
1 | 3486-3489 | 2
2
1
+xx
2 (
)
2
log x
x
3 1
log
x
x
x
+
4 sin
xsin (cos )
x
5 |
1 | 3487-3490 | (
)
2
log x
x
3 1
log
x
x
x
+
4 sin
xsin (cos )
x
5 sin (
) cos (
)
ax
b
ax
b
+
+
6 |
1 | 3488-3491 | 1
log
x
x
x
+
4 sin
xsin (cos )
x
5 sin (
) cos (
)
ax
b
ax
b
+
+
6 ax
+b
7 |
1 | 3489-3492 | sin
xsin (cos )
x
5 sin (
) cos (
)
ax
b
ax
b
+
+
6 ax
+b
7 2
x
x +
8 |
1 | 3490-3493 | sin (
) cos (
)
ax
b
ax
b
+
+
6 ax
+b
7 2
x
x +
8 2
1
2
x
x
+
9 |
1 | 3491-3494 | ax
+b
7 2
x
x +
8 2
1
2
x
x
+
9 2
(4
2)
1
x
x
x
+
+
+
10 |
1 | 3492-3495 | 2
x
x +
8 2
1
2
x
x
+
9 2
(4
2)
1
x
x
x
+
+
+
10 1
x –
x
11 |
1 | 3493-3496 | 2
1
2
x
x
+
9 2
(4
2)
1
x
x
x
+
+
+
10 1
x –
x
11 4
x
x +
, x > 0
12 |
1 | 3494-3497 | 2
(4
2)
1
x
x
x
+
+
+
10 1
x –
x
11 4
x
x +
, x > 0
12 1
3
5
3
(
x –1)
x
13 |
1 | 3495-3498 | 1
x –
x
11 4
x
x +
, x > 0
12 1
3
5
3
(
x –1)
x
13 2
3 3
(2
3
)
x
+x
14 |
1 | 3496-3499 | 4
x
x +
, x > 0
12 1
3
5
3
(
x –1)
x
13 2
3 3
(2
3
)
x
+x
14 1
x(log )m
x
, x > 0,
≠1
m
15 |
1 | 3497-3500 | 1
3
5
3
(
x –1)
x
13 2
3 3
(2
3
)
x
+x
14 1
x(log )m
x
, x > 0,
≠1
m
15 2
9
4
x
– x
16 |
1 | 3498-3501 | 2
3 3
(2
3
)
x
+x
14 1
x(log )m
x
, x > 0,
≠1
m
15 2
9
4
x
– x
16 2
3
ex
+
17 |
1 | 3499-3502 | 1
x(log )m
x
, x > 0,
≠1
m
15 2
9
4
x
– x
16 2
3
ex
+
17 x2
x
e
INTEGRALS 305
18 |
1 | 3500-3503 | 2
9
4
x
– x
16 2
3
ex
+
17 x2
x
e
INTEGRALS 305
18 1
2
1
tan–
x
e
+x
19 |
1 | 3501-3504 | 2
3
ex
+
17 x2
x
e
INTEGRALS 305
18 1
2
1
tan–
x
e
+x
19 2
2
1
1
x
x
e
–
e
+
20 |
1 | 3502-3505 | x2
x
e
INTEGRALS 305
18 1
2
1
tan–
x
e
+x
19 2
2
1
1
x
x
e
–
e
+
20 2
2
2
2
x
–
x
x
–
x
e
– e
e
e
+
21 |
1 | 3503-3506 | 1
2
1
tan–
x
e
+x
19 2
2
1
1
x
x
e
–
e
+
20 2
2
2
2
x
–
x
x
–
x
e
– e
e
e
+
21 tan2 (2x – 3)
22 |
1 | 3504-3507 | 2
2
1
1
x
x
e
–
e
+
20 2
2
2
2
x
–
x
x
–
x
e
– e
e
e
+
21 tan2 (2x – 3)
22 sec2 (7 – 4x)
23 |
1 | 3505-3508 | 2
2
2
2
x
–
x
x
–
x
e
– e
e
e
+
21 tan2 (2x – 3)
22 sec2 (7 – 4x)
23 1
2
sin
1
– x
– x
24 |
1 | 3506-3509 | tan2 (2x – 3)
22 sec2 (7 – 4x)
23 1
2
sin
1
– x
– x
24 2cos
3sin
6cos
4sin
x –
x
x
x
+
25 |
1 | 3507-3510 | sec2 (7 – 4x)
23 1
2
sin
1
– x
– x
24 2cos
3sin
6cos
4sin
x –
x
x
x
+
25 2
2
1
cos
(1
tan )
x
–
x
26 |
1 | 3508-3511 | 1
2
sin
1
– x
– x
24 2cos
3sin
6cos
4sin
x –
x
x
x
+
25 2
2
1
cos
(1
tan )
x
–
x
26 cos
x
x
27 |
1 | 3509-3512 | 2cos
3sin
6cos
4sin
x –
x
x
x
+
25 2
2
1
cos
(1
tan )
x
–
x
26 cos
x
x
27 sin 2 cos 2
x
x
28 |
1 | 3510-3513 | 2
2
1
cos
(1
tan )
x
–
x
26 cos
x
x
27 sin 2 cos 2
x
x
28 cos
1
sin
x
x
+
29 |
1 | 3511-3514 | cos
x
x
27 sin 2 cos 2
x
x
28 cos
1
sin
x
x
+
29 cot x log sin x
30 |
1 | 3512-3515 | sin 2 cos 2
x
x
28 cos
1
sin
x
x
+
29 cot x log sin x
30 sin
1
cos
x
x
+
31 |
1 | 3513-3516 | cos
1
sin
x
x
+
29 cot x log sin x
30 sin
1
cos
x
x
+
31 (
)
2
sin
1
cos
x
x
+
32 |
1 | 3514-3517 | cot x log sin x
30 sin
1
cos
x
x
+
31 (
)
2
sin
1
cos
x
x
+
32 1
1
cot x
+
33 |
1 | 3515-3518 | sin
1
cos
x
x
+
31 (
)
2
sin
1
cos
x
x
+
32 1
1
cot x
+
33 1
1
–tan
x
34 |
1 | 3516-3519 | (
)
2
sin
1
cos
x
x
+
32 1
1
cot x
+
33 1
1
–tan
x
34 tan
sin
cos
x
x
x
35 |
1 | 3517-3520 | 1
1
cot x
+
33 1
1
–tan
x
34 tan
sin
cos
x
x
x
35 (
)
2
1
log x
x
+
36 |
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