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?