In an isosceles triangle $XYZ$, the measure of angle $X$ is $100°$. What is the measure of angle $Y$?
Answer:
A
Explanation
The correct answer is Choice A.
Find the measure of angle $Y$ using the sum of all internal angles of a triangle.
Choice B incorrect the sum of the three angles adds up to more than $180^{\circ}$.
Choices C and D is incorrect because the sum of the angles $X$ and $Y$ alone adds up to $180^{\circ}$ or more.
✨ Expert's Tip ✨
An alternate method is to add the angle given in each choice to the two known angles to check if they add up to $180^{\circ}$.