Question

The base angle of an isosceles triangle is 45. What is the measure of the vertex angle?

Answer 1

First, let's picture the problem:

Let's label the unknown vertex angle as x

Remember that the sum of angles in a triangle is 180

Hence,

`\begin{gathered} 45^0+45^0+x=180^0 \\ x=180^0\text{ - }90^0 \\ =90^0 \end{gathered}`

For an isosceles triangle, the base angles are equal