Integration Techniques: Substitution, Partial Fractions, and Special Functions, Assignments of Mathematics

Various techniques for integrating functions, including substitution, partial fractions, and special functions. It covers integration of basic functions, integrals with limits of integration, and integrals of trigonometric functions. The document also includes formulas for integrals of sin, cos, and tan functions.

Typology: Assignments

2019/2020

Uploaded on 09/30/2020

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[
f
(
x
)
]
n
f
'
(
x
)
xⅆx
*(where n is +ve / –ve)
Put
f
(
x
)
=
t
dt=f
'
(
x
)
xⅆx
----------------------------------------------------------------------
-
(
ax +b
) (
cx +d
)
ndx
*(where n is +ve /–ve)
Write
ax +b=λ
(
cx +d
)
+μ
; Put
(
cx +d
)
=
t
----------------------------------------------------------------------
-
xⅆx
a x
2
+bx +c
,
,
a x
2
+bx+c dx
Express
(a x
2
+bx +c)
=
(z2± α 2)
; α =
constant
----------------------------------------------------------------------
-
(px+q)
a x2+bx +cdx
,
dx
,
(px+q)
a x
2
+bx +c dx
Write
(px+q)= A
{
ⅆx
xⅆx
(
a x
2
+bx +c
)
}
+B
----------------------------------------------------------------------
-
sinpxcosqx dx
If atleast one is odd of
p
&
q
spare one of which is odd, and substitute
the other as z and write whole in terms of
z
If both are even of
p
&
q
Use sin 2A, cos 2A formulas to simplify
If (
p+q) is –ve even integer
divide numerator & denominator by sin
kx (or cos kx); k =
(m+n) , then
substitute cot x = z (or tan x = z)
----------------------------------------------------------------------
-
sin mx sin nx dx
,
sin mx cos nx dx
,
or
cos mx cos nx dx
Use : 2
sin Asin B
=
cos (AB)−cos (A+B)
2
sin Acos B
=
sin
(
A+B
)
+sin
(
AB
)
2
cos Asin B
=
sin
(
A+B
)
sin
(
AB
)
2
cos Acos B
=
cos (AB)+cos (A+B)
----------------------------------------------------------------------
-
xⅆx
asin
2
x+bcos
2
x+c
,
xⅆx
a+bsin
2
⁡x
,
xⅆx
a+bcos2⁡x
,
xⅆx
(
asin ⁡x+bcos ⁡x
)
2
*(where c may be zero)
Divide numerator & denominator by
cos
2
x
Put
tan x=z
xⅆx
asin x +bcos x +c
,
xⅆx
a+bsin x
,
xⅆx
a+bcos x
*(where c may be zero)
Put
sin ⁡x=
2 tan x
2
1+tan
2
x
2
and
cos ⁡x=
1tan
2
x
2
1+tan
2
x
2
Simplify, then put
tan
x
2
¿z
dz=1
2sec
2
x
2xⅆx
----------------------------------------------------------------------
-
asin x +bcos x+c
lsin x+mcos x+nxⅆx
For
c = n = 0
,
Write numerator =
A
{
ⅆx
xⅆx
(deno)}
+B
(deno)
For non-zero
c
&
n
,
Write numerator =
A
{
ⅆx
xⅆx
(deno)}
+B
(deno) + C
----------------------------------------------------------------------
-
Method of Partial Integration:
P(x)
Q(x)
xⅆx
where degree of
P
(
x
)
<Q(x)
Break
Q(x)
into factors
(
xa
)
,
(
xb
)
,
(
xc
)
Write
P(x)
Q(x)
=
A
(xa)
+
B
(xb)+C
(xc)
*deno =
denominator
pf2

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 ∫[ f ( x ) ]

n f ' ( x) ⅆxx *(where n is^ +ve / –ve) Put f ( x ) = t ⇒ (^) dt=f '^ ( (^) x ) (^) ⅆxx


 ∫( ax +b ) ( cx + d ) n dx *(where n is +ve /–ve) Write ax +b=λ ( cx + d )+ μ ; Put ( cx +d ) = t


 ∫ ⅆxx a x 2 +bx +c ,∫ ⅆxx √a^ x 2 +bx +c ,∫√a^ x 2

  • bx+ c dx Express (^) (a x^2 +bx +c) = (^) ( z^2 ± α^2 ) ; α = constant

 ∫ ( px+ q) a x 2 +bx +c dx (^) , ∫ (px +q ) √a^ x 2 +bx +c

dx ,

∫(^ px+^ q)^ √a^ x 2 +bx +c dx Write (^ px+q)=^ A^ { ⅆx ⅆx x ( (^) a x^2 +bx +c ) (^) } + B


 ∫ (^) sinp^ x cosq^ x dx If atleast one is odd of p & q ⇒ spare one of which is odd, and substitute the other as z and write whole in terms of z If both are even of p & q ⇒ Use sin 2A, cos 2A formulas to simplify If ( p+q) is –ve even integer ⇒ divide numerator & denominator by sin kx (or cos kx); k = – (m+n) , then substitute cot x = z (or tan x = z)


 ∫sin^ mx^ sin^ nx^ dx^ , ∫sin^ mx^ cos^ nx^ dx , or ∫cos mx cosnx dx Use : 2sin A sin B= cos ( A−B)−cos( A+ B) 2 sin A cos B= sin ( A+ B) +sin ( A−B ) 2 cos A sin B= sin ( A+ B)−sin ( A−B) 2 cos A cos B= cos ( A−B)+cos (A + B)


 ∫ ⅆxx a sin 2 x +b cos 2 x +c , ∫ ⅆxx a+b sin 2 x

∫ ⅆxx a+b cos 2 x , ∫ ⅆxx ( a sin x+b cos x ) 2 *(where c may be zero) Divide numerator & denominator by (^) cos^2 x Put tan x=z  ∫ ⅆxx asin x +bcos x +c ,^ ∫^ ⅆxx a+bsin x ,^ ∫ ⅆx x a+bcos x *(where c may be zero) Put sin^ x= 2 tan x 2 1 +tan^2 x 2 and cos^ x^ = 1 −tan 2 x 2 1 + tan^2 x 2 Simplify, then put tan x 2 ¿ z ⇒ dz=

sec 2 x 2 ⅆxx


 ∫ asin x +bcos x+ c lsin x +mcos x+n ⅆxx For c = n = 0 ,

⇒ Write numerator = A^ {

ⅆx ⅆx x

(deno)} +^ B

(deno) For non-zero c & n ,

⇒ Write numerator = A^ {

ⅆx ⅆx x

(deno)} +^ B

(deno) + C

 Method of Partial Integration: ∫ P( x ) Q(x) ⅆxx (^) where degree of P ( x )<Q ( x) Break Q(x) into factors ( x−a ) ,( x−b ) ,( x−c ) … Write P( x ) Q(x)

A

( x−a)

B

(x−b)

C

(x−c ) *deno = denominator

A

(x−a)

B

(x−a)

2 +^

C

( x−b) (for repetitive factors) =

A

(x−a)

Bx+C (b x 2 +c x +d ) (for quadratic factors)


(x 2 ± 1 ) ⅆxx x 4

  • λx 2
  • 1

ⅆxx x 4

  • λx 2
  • 1 Divide numerator & denominator by (^) x^2

Express denominator as : (x ±

x )

2 ± k 2

Put (x^ ±^

x )^

= t ⇒ (^) dt=¿ ¿ x 2 1 x 2 ⅆxx


ⅆxx

(ax +b)√ px +q ,^ ∫^

ⅆxx (a x 2

+bx +c)√ px +q

Put ( (^) px+ q) (^) =t^2 and simplify.

ⅆxx ( px+ q) √a x 2 +bx +c Put (^ px+q)^ =¿^

t and simplify.


 Special substitutions: a 2 + x (^2) Put x=a tan θ or a cot θ a^2 −x^2 Put^ x=a^ sin^ θ^ or^ a^ cos^ θ x 2 −a (^2) Put x=a sec θ or a cosec θ

a ± x a x Put x=a cos 2 θ