Question

if sinθ+cosθ=0 thenθ=?

Answer 1

suppose that theta equal to alfa

$sin \alpha = - cos \alpha \\ \\ cos \alpha = \cos( \frac{\pi}{2 } + \alpha ) \\ \\ \alpha = 2n\pi - \frac{\pi}{2} - \alpha \\ \\ \alpha = n\pi - \frac{\pi}{4}$