Maxima and MinimaHard

Question

The number of values of x where the function f(x) = 2(cos3x + cos √3 x) attains its maximum, is -

Options

A.1
B.2
C.0
D.infinite

Solution

f(x) = 2(cos 3x + cos √ 3x)
= 4 cos x. cos x ≤ 4
and it is equal to 4 when both
cos x and  cos x are equal to 1
for a value of x.
This is possible only, when x = 0.
f(x) = 2(cos 3x + cos √ 3x)
= 4 cos x. cos x ≤ 4
and it is equal to 4 when both
cos x and  cos x are equal to 1
for a value of x.
This is possible only, when x = 0.

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