Question

find value of cos -1125

Answer 1

$\cos( - 1125) \\ = \cos( - 6\pi - \frac{\pi}{4} ) \\ = \cos( \frac{ - \pi}{4} )$
It lies in fourth quadrant Hence
$\cos( \frac{\pi}{4} ) \\ = \frac{1}{ \sqrt{2} }$