(1) Because BE//CD, the angle ADC is the angle BEtween AD and Be, because AC=BC=CD. ABC⊥ bottom side. So the angle ACD=90 degrees. So the angle ADC is 45 degrees.

Because the edge ABC⊥ bottom BCDE found the midpoint F of CB, and AF⊥BCDE connected CE and DF to G, CH⊥GF solved the equation of CG FG by similarity method, and obtained the cosine three perpendicular theorem of angle CGH of CH HG. This is the solution.

(2) get AF FD AF/FD from 1.

(3) Make AI⊥DE angle AIF, that is, make two vertical lines BD to calculate each side.