# How do you prove sinx + cosx = -1?

This is easy to see with a few test values of $x$
$x = 0 \rightarrow \sin \left(0\right) + \cos \left(0\right) = 1 \ne - 1$
$x = \frac{\pi}{4} \rightarrow \sin \left(\frac{\pi}{4}\right) + \cos \left(\frac{\pi}{4}\right) = \sqrt{2}$