Question

f(x) = coses x in (-π, 0) has a maxima at

A. x = 0

B. x = -π/4

C. x = -π/3

D. x = -π/2

Answer 1

Answer is : D. x = -π/2

We can go through options for this question

Option a is wrong because 0 is not included in (-π,0)

At x = -π/4 value of f(x) is -√2 = -1.41

At x = -π/3 value of f(x) is -2.

At x = -π/2 value of f(x) is -1.

∴ f(x) has max value at x = -π/2.

Which is -1.