Prove that the function f given by f (x) = log |cos x| is strictly decreasing on
and strictly increasing on
.
It is given that f (x) = log |cos x|
In interval
, f’(x) = -tanx < 0
Therefore, f is strictly decreasing on
.
In interval
, f’(x) = -tanx > 0
Therefore, f is strictly increasing in
.
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