If the measure of ABC = 180o, and the length of AD and DC are equal, which is the measure of

Question

If the measure of ABC = 180o, and the length of AD  and DC are equal, which is the measure of <ACD?

anonymous · Answer

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anonymous · Answer

Possible answers

A. 30o 
B. 45o
C. 90o
D. 180o

anonymous · Answer

I think i just answered this question, but here it is again:

This triangle is an isosceles triangle because the lengths AD and DC are equal,  

This triangle is also a right triangle because when the longest side is the diameter and the other point of the triangle is on the circle, a right triangle will be created.

An isosceles right triangle has the side lengths 90-45-45, and the angle ACD in this problem would be 45 degrees.