Isosceles and Equilateral Triangles

Front

What is an isosceles triangle?

Back

An isosceles triangle is a triangle that has at least two sides of equal length.

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 to 60°.

Front

What is the sum of the interior angles of a triangle?

Back

The sum of the interior angles of a triangle is always 180°.

Front

If two angles of a triangle are equal, what type of triangle is it?

Back

It is an isosceles triangle.

Front

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

Back

The vertex angle is 100°.

Front

What is the formula for the perimeter of an equilateral triangle?

Back

The perimeter P of an equilateral triangle with side length a is P = 3a.

Front

If the perimeter of an equilateral triangle is 21 meters, what is the length of each side?

Back

Each side is 7 meters.

Front

What is the relationship between the sides and angles in an isosceles triangle?

Back

The angles opposite the equal sides are also equal.

Front

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

Back

Subtract the sum of the known angles from 180°.

Front

If one angle of a triangle is 90°, what type of triangle is it?

Back

It is a right triangle.