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Question: f(x)=\(\int_{0}^{x}{(t^{2}–1)}\cos tdt,x \in (0,\pi)\), f(x) attains local minimum value at –...

f(x)=0x(t21)costdt,x(0,π)\int_{0}^{x}{(t^{2}–1)}\cos tdt,x \in (0,\pi), f(x) attains local minimum value at –

A

x = p/2

B

x = 1

C

x = 3p/2

D

None

Answer

x = 1

Explanation

Solution

f '(x) ̃ (x2 – 1) cos x = 0

x = 1, x = p/2

f.''(x) = cos x. 2x + (x2 – 1) (– sin x)

f.''(x) = 2 cos x > 0 7 minimum