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. 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

If an isosceles triangle has a base angle measuring 40°, what is the vertex angle?

Back

100°

Front

In an isosceles triangle, if two sides are congruent, what can be said about the angles opposite those sides?

Back

The angles opposite the congruent sides are also congruent.

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

Back

It is a right triangle.

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

What is the relationship between the sides and angles in a triangle?

Back

In a triangle, the larger the angle, the longer the opposite side.

Front

If two angles of a triangle measure 70° and 50°, what is the measure of the third angle?

Back

The third angle measures 60°.

Front

What is the formula for the area of a triangle?

Back

Area = 1/2 * base * height.