Page 1
1
Revision Notes
Application of Integrals
Definite Integration
1. Definition:
If ( ) F x is an antiderivative of ( ) f x , then ( ) ( ) - F b F a is known as the definite integral of
( ) fx from a to b , such that the variable x, takes any two independent values say a and b .
This is also denoted as
b
a
f(x)dx
?
.
Thus ( ) ( )
b
a
f(x)dx F b F a =-
?
, The numbers a and b are called the limits of integration; a is
the lower limit and b is the upper limit.
2. Properties of Definite Integrals:
I.
ba
ab
f(x)dx= f(x) -
??
II.
ba
ab
f(x)dx= f(y)dy
??
III.
b c b
a a c
f(x)dx= f(x)dx+ f(x)dx
? ? ?
, where c may or may not lie between a and b .
IV .
aa
00
f(x)dx= f(a x)dx -
??
Page 2
1
Revision Notes
Application of Integrals
Definite Integration
1. Definition:
If ( ) F x is an antiderivative of ( ) f x , then ( ) ( ) - F b F a is known as the definite integral of
( ) fx from a to b , such that the variable x, takes any two independent values say a and b .
This is also denoted as
b
a
f(x)dx
?
.
Thus ( ) ( )
b
a
f(x)dx F b F a =-
?
, The numbers a and b are called the limits of integration; a is
the lower limit and b is the upper limit.
2. Properties of Definite Integrals:
I.
ba
ab
f(x)dx= f(x) -
??
II.
ba
ab
f(x)dx= f(y)dy
??
III.
b c b
a a c
f(x)dx= f(x)dx+ f(x)dx
? ? ?
, where c may or may not lie between a and b .
IV .
aa
00
f(x)dx= f(a x)dx -
??
2
V .
bb
aa
f(x)dx= f(a+b x)dx -
??
Note:
a.
a
0
f(x) a
dx=
f(x)+f(a x) 2 -
?
b.
b
a
f(x) b a
dx=
f(x)+f(a+b x) 2
-
-
?
VI.
2a a a
0 0 0
f(x)dx= f(x)dx+ f(2a x)dx -
? ? ?
a
0
0 if f(2a x) f(x)
=
2 f(x)dx if f(2a x) f(x)
- = - ??
??
??
-=
??
??
?
VII.
a
a
0
-a
2 f(x)dx if f( x) f(x)i.e.f(x)iseven
f
(x)dx
0 if f( x) f( x)i.e.f(x)isodd
??
-=
??
=
??
??
- = -
??
?
?
VIII. If f(x) is a periodic function of period (Tex translation failed) , i.e. f(a x) f(x) += , then
a.
na a
00
f(x)dx n f(x)dx =
??
b. ( )
na a
00
f(x)dx n 1 f(x)dx =-
??
Page 3
1
Revision Notes
Application of Integrals
Definite Integration
1. Definition:
If ( ) F x is an antiderivative of ( ) f x , then ( ) ( ) - F b F a is known as the definite integral of
( ) fx from a to b , such that the variable x, takes any two independent values say a and b .
This is also denoted as
b
a
f(x)dx
?
.
Thus ( ) ( )
b
a
f(x)dx F b F a =-
?
, The numbers a and b are called the limits of integration; a is
the lower limit and b is the upper limit.
2. Properties of Definite Integrals:
I.
ba
ab
f(x)dx= f(x) -
??
II.
ba
ab
f(x)dx= f(y)dy
??
III.
b c b
a a c
f(x)dx= f(x)dx+ f(x)dx
? ? ?
, where c may or may not lie between a and b .
IV .
aa
00
f(x)dx= f(a x)dx -
??
2
V .
bb
aa
f(x)dx= f(a+b x)dx -
??
Note:
a.
a
0
f(x) a
dx=
f(x)+f(a x) 2 -
?
b.
b
a
f(x) b a
dx=
f(x)+f(a+b x) 2
-
-
?
VI.
2a a a
0 0 0
f(x)dx= f(x)dx+ f(2a x)dx -
? ? ?
a
0
0 if f(2a x) f(x)
=
2 f(x)dx if f(2a x) f(x)
- = - ??
??
??
-=
??
??
?
VII.
a
a
0
-a
2 f(x)dx if f( x) f(x)i.e.f(x)iseven
f
(x)dx
0 if f( x) f( x)i.e.f(x)isodd
??
-=
??
=
??
??
- = -
??
?
?
VIII. If f(x) is a periodic function of period (Tex translation failed) , i.e. f(a x) f(x) += , then
a.
na a
00
f(x)dx n f(x)dx =
??
b. ( )
na a
00
f(x)dx n 1 f(x)dx =-
??
3
c.
b+na b
na 0
f(x)dx f(x)dx =
??
, where bR ?
d.
b+a
b
f(x)dx
?
independent of b .
e.
b+na a
b0
f(x)dx n f(x)dx =
??
, where n1 ?
IX. If f(x) 0 ? on the interval ? ?
a,b , then
b
a
f(x)dx 0 ?
?
.
X. If f(x) g(x) ? on the interval ? ?
a,b , then
bb
aa
f(x)dx g(x)dx ?
??
XI.
bb
aa
f(x)dx f(x) dx ?
??
XII. If f(x) is continuous on ? ?
a,b , m is the least and M is the greatest value of f(x) on
? ?
a,b , then
( )
b
a
m b a f(x)dx M(b a) - ? ? -
?
XIII. For any two functions f(x) and g(x) , integral on the interval ? ?
a,b , the Schwarz-
Bunyakovsky inequality holds
b b b
22
a a a
f(x).g(x)dx f (x)dx. g (x)dx ?
? ? ?
Page 4
1
Revision Notes
Application of Integrals
Definite Integration
1. Definition:
If ( ) F x is an antiderivative of ( ) f x , then ( ) ( ) - F b F a is known as the definite integral of
( ) fx from a to b , such that the variable x, takes any two independent values say a and b .
This is also denoted as
b
a
f(x)dx
?
.
Thus ( ) ( )
b
a
f(x)dx F b F a =-
?
, The numbers a and b are called the limits of integration; a is
the lower limit and b is the upper limit.
2. Properties of Definite Integrals:
I.
ba
ab
f(x)dx= f(x) -
??
II.
ba
ab
f(x)dx= f(y)dy
??
III.
b c b
a a c
f(x)dx= f(x)dx+ f(x)dx
? ? ?
, where c may or may not lie between a and b .
IV .
aa
00
f(x)dx= f(a x)dx -
??
2
V .
bb
aa
f(x)dx= f(a+b x)dx -
??
Note:
a.
a
0
f(x) a
dx=
f(x)+f(a x) 2 -
?
b.
b
a
f(x) b a
dx=
f(x)+f(a+b x) 2
-
-
?
VI.
2a a a
0 0 0
f(x)dx= f(x)dx+ f(2a x)dx -
? ? ?
a
0
0 if f(2a x) f(x)
=
2 f(x)dx if f(2a x) f(x)
- = - ??
??
??
-=
??
??
?
VII.
a
a
0
-a
2 f(x)dx if f( x) f(x)i.e.f(x)iseven
f
(x)dx
0 if f( x) f( x)i.e.f(x)isodd
??
-=
??
=
??
??
- = -
??
?
?
VIII. If f(x) is a periodic function of period (Tex translation failed) , i.e. f(a x) f(x) += , then
a.
na a
00
f(x)dx n f(x)dx =
??
b. ( )
na a
00
f(x)dx n 1 f(x)dx =-
??
3
c.
b+na b
na 0
f(x)dx f(x)dx =
??
, where bR ?
d.
b+a
b
f(x)dx
?
independent of b .
e.
b+na a
b0
f(x)dx n f(x)dx =
??
, where n1 ?
IX. If f(x) 0 ? on the interval ? ?
a,b , then
b
a
f(x)dx 0 ?
?
.
X. If f(x) g(x) ? on the interval ? ?
a,b , then
bb
aa
f(x)dx g(x)dx ?
??
XI.
bb
aa
f(x)dx f(x) dx ?
??
XII. If f(x) is continuous on ? ?
a,b , m is the least and M is the greatest value of f(x) on
? ?
a,b , then
( )
b
a
m b a f(x)dx M(b a) - ? ? -
?
XIII. For any two functions f(x) and g(x) , integral on the interval ? ?
a,b , the Schwarz-
Bunyakovsky inequality holds
b b b
22
a a a
f(x).g(x)dx f (x)dx. g (x)dx ?
? ? ?
4
XIV . If a function f(x) is continuous on the interval ? ?
a,b , then there exists a point ( ) c a,b ?
such that
b
a
f(x)dx f(c)(b a) =-
?
, where a c b ?? .
3. Differentiation Under Integral Sign:
Newton Leibnitz’s Theorem:
Given that x has two differentiable functions, g(x) and h(x) , where ? ?
x a,b ? and f is
continuous in that interval, then
? ? ? ? ? ? ? ?
h(x)
g(x)
d d d
f(t)dt h(x) .f h(x) g(x) .f g(x)
dx dx dx
??
=-
??
??
??
?
4. Definite Integral as a Limit of Sum:
Let f(x) be a continuous real valued function defined on the closed interval ? ?
a,b which is
divided into n parts as shown in figure.
Page 5
1
Revision Notes
Application of Integrals
Definite Integration
1. Definition:
If ( ) F x is an antiderivative of ( ) f x , then ( ) ( ) - F b F a is known as the definite integral of
( ) fx from a to b , such that the variable x, takes any two independent values say a and b .
This is also denoted as
b
a
f(x)dx
?
.
Thus ( ) ( )
b
a
f(x)dx F b F a =-
?
, The numbers a and b are called the limits of integration; a is
the lower limit and b is the upper limit.
2. Properties of Definite Integrals:
I.
ba
ab
f(x)dx= f(x) -
??
II.
ba
ab
f(x)dx= f(y)dy
??
III.
b c b
a a c
f(x)dx= f(x)dx+ f(x)dx
? ? ?
, where c may or may not lie between a and b .
IV .
aa
00
f(x)dx= f(a x)dx -
??
2
V .
bb
aa
f(x)dx= f(a+b x)dx -
??
Note:
a.
a
0
f(x) a
dx=
f(x)+f(a x) 2 -
?
b.
b
a
f(x) b a
dx=
f(x)+f(a+b x) 2
-
-
?
VI.
2a a a
0 0 0
f(x)dx= f(x)dx+ f(2a x)dx -
? ? ?
a
0
0 if f(2a x) f(x)
=
2 f(x)dx if f(2a x) f(x)
- = - ??
??
??
-=
??
??
?
VII.
a
a
0
-a
2 f(x)dx if f( x) f(x)i.e.f(x)iseven
f
(x)dx
0 if f( x) f( x)i.e.f(x)isodd
??
-=
??
=
??
??
- = -
??
?
?
VIII. If f(x) is a periodic function of period (Tex translation failed) , i.e. f(a x) f(x) += , then
a.
na a
00
f(x)dx n f(x)dx =
??
b. ( )
na a
00
f(x)dx n 1 f(x)dx =-
??
3
c.
b+na b
na 0
f(x)dx f(x)dx =
??
, where bR ?
d.
b+a
b
f(x)dx
?
independent of b .
e.
b+na a
b0
f(x)dx n f(x)dx =
??
, where n1 ?
IX. If f(x) 0 ? on the interval ? ?
a,b , then
b
a
f(x)dx 0 ?
?
.
X. If f(x) g(x) ? on the interval ? ?
a,b , then
bb
aa
f(x)dx g(x)dx ?
??
XI.
bb
aa
f(x)dx f(x) dx ?
??
XII. If f(x) is continuous on ? ?
a,b , m is the least and M is the greatest value of f(x) on
? ?
a,b , then
( )
b
a
m b a f(x)dx M(b a) - ? ? -
?
XIII. For any two functions f(x) and g(x) , integral on the interval ? ?
a,b , the Schwarz-
Bunyakovsky inequality holds
b b b
22
a a a
f(x).g(x)dx f (x)dx. g (x)dx ?
? ? ?
4
XIV . If a function f(x) is continuous on the interval ? ?
a,b , then there exists a point ( ) c a,b ?
such that
b
a
f(x)dx f(c)(b a) =-
?
, where a c b ?? .
3. Differentiation Under Integral Sign:
Newton Leibnitz’s Theorem:
Given that x has two differentiable functions, g(x) and h(x) , where ? ?
x a,b ? and f is
continuous in that interval, then
? ? ? ? ? ? ? ?
h(x)
g(x)
d d d
f(t)dt h(x) .f h(x) g(x) .f g(x)
dx dx dx
??
=-
??
??
??
?
4. Definite Integral as a Limit of Sum:
Let f(x) be a continuous real valued function defined on the closed interval ? ?
a,b which is
divided into n parts as shown in figure.
5
The point of division on x- axis are
( ) a,a h,a 2h.....a n 1 h,a nh, + + + - + where
ba
h
n
-
= .
Let
n
S denotes the area of these n rectangles.
Then, ( ) ( ) ( ) ( )
n
S hf(a) hf a h hf a 2h .... hf a n 1 h = + + + + + + + -
Clearly,
n
S is area very close to the area of the region bounded by
Curve y f(x), = x- axis and the ordinates xa = , xb = .
Hence
b
n
n
a
lim f(x)dx S
??
=
?
b
n-1
n
r0
a
fa lim (x)dx hf( +rh)
??
=
=
?
?
( )
n-1
n
r0
b
lim
ar
ba
fa
nn
??
=
?? -
- ??
=+
??
??
??
??
?
Note:
(a) We can also write
( ) ( ) ( )
n
S hf a h hf a 2h ..... hf a nh = + + + + + +
b
n
n
r1
a
b a b a
f(x)dx f a r
n
lim
n
??
=
?? -- ? ? ? ?
=+
? ? ? ? ??
? ? ? ?
??
?
?
(b) If
1
n1
n
r0
0
1r
a 0,b 1, f(x)dx f l
n
m
n
i
-
??
=
??
= = =
??
??
?
?
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