Test:36 QNo:4

doubt

find maximum value of y=cosx +logcosx in(-∩/2,∩2)

\frac{dy}{dx} = -sinx - tanx
in (-\pi /2 , 0) .. sinx and tanx are negative. So, dy/dx is positive hence the function increases.
In (0,\pi /2) sinx and tanx are positive hence dy/dx is negative hence the function decreases.

So, max value of the function is at x = 0
which is (1 + 0) = 1