Hi, I need some help with this insanely difficult 3D trigonometry that I've been stuck on for over 20 minutes.
Draw separate diagrams of the triangles KBF,KCG and KCB. IN triangle KBF tan30=h/BK. In triangle KCG tan45=h/CK. In triangle BCK use cosine rule to express BK^2
Substitute BK and CK from the first two into the last one and solve a quadratic to get the result.