## 100 degree Isosceles Triangle

Given an isosceles 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 measure of
angle BCD? Prove your results by geometric reasoning, rather than measuring.

Note: There can be several different approaches
to this problem. Geometric arguments are preferred rather than using trigonometry.

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Usually, a solution to a problem such as this
requires some auxiliary constructions.

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

Find alternative solutions or compare your solution
to the solutions of others to see alternative approaches.

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