# How do you find θ, if 0 < θ < 360 and cos theta = -1/sqrt2  and theta in in Qii?

Find x knowing $\cos x = - \frac{1}{\sqrt{2}}$
Ans: $\frac{3 \pi}{4}$
Trig table gives -> $\cos x = - \frac{1}{\sqrt{2}} = - \frac{\sqrt{2}}{2}$ --> $x = \frac{3 \pi}{4}$ or 135 deg