# Math Help - modulus of -cos2x

1. ## modulus of -cos2x

I'm not sure how to prove that the modulus of -cos2x in the range 0<x<pi/2 is less than 1.

2. You should know that

$-1 \leq -\cos{2x} \leq 1$

so

$|-\cos{2x}| \leq 1$.

You should also find the values for which $-\cos{2x} = \pm 1$, to show that they occur outside the domain $0 < x < \frac{\pi}{2}$.