Let ABCD is a tetragon with its cyclic (outer circle). Diagonal BD bisects angle ABC. The intersection point of BD and AC diagonals is point E. BC = 20, CD = 15, CE=12.
Please help me find AD, ED, angle BCD and the area of tetragon ABCD.
I have tried to find the relationship between the half angles of B, with side AD, but in fact I could not find any.