## Problem: 100 degree Isosceles Triangle

Given an isoscles triangle ABC with AB = AC
and the measure of angle BAC = 100 degrees. Extend AB to point
D such that AD = BC. Now draw segment CD. What is the size of
angle BCD?

Note: There can be several different approaches
to this problem.

Ususally, a solution to a problem such as this
requires some auxilliary constructions.

Do you want a **Hint** for one auxillary
construction?