If triangle abc is isosceles, what is the value of ∠a?

a. 78°
b. 68°
c. 58°
d. 102°

Hello there, and thank you for posting your question here on .

Short A: 78 °

Why?

Well, when we have a triangle, we have to add up all the angles to be able to have 180°. So, we have an isosceles triangle, we know that an isosceles triangle has two equal sides. We have two unknown sides, but we know that side C is also 51°. When we add both of them up, we have 102. Which of the answer choices make it add up to 180? 78.

Hope this helped you! ♥