Can someone please check that I've got the correct answers as they don't appear to fit.

Q: cos2x = -(√3)/2 -180<=x<=180

I've got 2x=210, 330, 570, 690

x=105, 165, 285, 345

We're currently learning about using CAST diagrams to solve trigonometric equations, so if any anyone can explain in terms of CAST diagrams I'd be grateful.