Question
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(t2–1)costdt,x∈(0,π), 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