In the figure below, given a triangle
ABC, the measure of the angles ACD, BCD, and ABC are a, 3a, and
120 - 2a. If BC = CE, find the measure of the angle CDE.

Geometric Art: Hyperbolic Kaleidoscope of problem 210

Auxiliary Line: A line, ray, or segment added to a diagram to help in a proof
or solution. View or post a solution.