Hi, it would mean so much to me if someone helped me with this problem:

Let B, A, and D be three consecutive vertices of a regular 18-gon. A regular heptagon is constructed on AB with a vertex C next to A. Find angle BCD.

Thanks!

I solve this using coordinates:

A = (1,0)

B = (0.924328, 0.471208)

C = (1.222783, -1.147542)

D = (0.924328, -0.471208)

==> angle BCD = 75 degrees

I got 80 degrees. Is that correct?