Isosceles & Equilateral Triangle Angle Theorems

Front

What is an isosceles triangle?

Back

An isosceles triangle is a triangle that has at least two sides of equal length. The angles opposite these sides are also equal.

Front

What is an equilateral triangle?

Back

An equilateral triangle is a triangle in which all three sides are of equal length and all three angles are equal, each measuring 60°.

Front

What is the sum of the angles in any triangle?

Back

The sum of the angles in any triangle is always 180°.

Front

Back

Front

Back

Front

How do you find the measure of an unknown angle in an isosceles triangle?

Back

Front

What is the relationship between the angles in an equilateral triangle?

Back

All angles in an equilateral triangle are equal, each measuring 60°.

Front

If two angles of a triangle are 40° and 60°, what is the measure of the third angle?

Back

Front

In an isosceles triangle, if the vertex angle is 40°, what are the measures of the base angles?

Back

Front

What is the formula to find the angles in an isosceles triangle?

Back