Prove that the function `f(x)=cosx` is strictly increasing in `(pi,\ 2pi)`

Prove that the function f(x)=cos x is strictly increasing in (pi,2 pi)

Prove that the function f(x)=cos x is strictly decreasing in (0,pi)

f(x) = cos x is strictly increasing in (pi,2pi)

Prove that the function f(x)=cosx is strictly decreasing in (0,\ pi)

Prove that the function f(x)=logsinx is strictly increasing in (0,pi/2) and strictly decreasing in (pi/2,pi)

Which one of the following is true? For the function f(x)= cos x f is strictly increasing in (pi, 2pi)

Is the function f(x) = cos x strictly increasing in (0, pi) ?

Prove that the function f(x)=cos^(2)x is strictly decreasing in (0,(pi)/(2))

Prove that the function f(x)=tanx-4x is strictly decreasing on (-pi//3,\ pi//3) .