Find the extreme values of `cos 2x+cos^2x`

Find the extreme values of sin 2x -cos 2x over R.

Find the extreme values of 11 cos^(2) x+ 15 sin x cos x- 9 sin^(2) x .

Find the extreme values of 3sin^(2)x+5cos^(2)x .

Find the extreme values of y = cos x(1+sin x), x in [0,2pi]

Find the extreme points of the following functions. Specify if the extremum is a maximum or minimum. Find the extreme values. y = sin x cos x,x in [pi/8, pi/2]

The extreme values of cos x cos((2pi)/(3)+x)cos((2pi)/(3)-x) is