Indefinite Integration 3 Question 5

5. If sinx1t2f(t)dt=1sinx,x(0,π/2), then f13 is

(a) 3

(b) 3

(c) 1/3

(d) None of these

(2005, 1M)

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Answer:

Correct Answer: 5. (a)

Solution:

  1. Since sinx1t2f(t)dt=1sinx, thus to find f(x).

On differentiating both sides using Newton Leibnitz formula

i.e. ddxsinx1t2f(t)dt=ddx(1sinx)

12f(1)(0)(sin2x)f(sinx)cosx=cosx

f(sinx)=1sin2x

For f13 is obtained when sinx=1/3

 i.e. f13=(3)2=3



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