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∫ 2 a 0 F ( X ) D X

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Question

`int_0^(2a)f(x)dx`

Sum
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Solution

We have.

`I=int_0^(2a)f(x)dx`

Then,

`I=int_0^af(x)dx+int_a^(2a)f(x)dx`

`I=int_0^af(x)dx+I_1 ......................["where, "I_1=int_a^(2a)f(x)dx]`

Let 2a - t = x then dx = - dt

If t = a ⇒ x = a

If t = 2a ⇒ x = 0

`I_1=int_0^(2a)f(x)dx=int_a^0f(2a-t)(-dt)=-int_a^0f(2a-t)dt`

`I_1=int_0^af(2a-t)dt=int_0^af(2a-x)dx`

`thereforeI=int_0^af(x)dx+int_0^af(2a-x)dx`

`I=int_0^af(x)dx+int_0^af(x)dx=2int_0^af(x)dx............................[f(2a-x=f(x))]`

Hence proved.

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Chapter 19: Definite Integrals - Exercise 20.5 [Page 95]

APPEARS IN

R.D. Sharma Mathematics Volume 1 and 2 [English] Class 12
Chapter 19 Definite Integrals
Exercise 20.5 | Q 40 | Page 95

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