Isosceles Triangles

Front

What is an isosceles triangle?

Back

An isosceles triangle is a triangle that has at least two sides of equal length and the angles opposite those sides are also equal.

Front

What are the properties of an isosceles triangle?

Back

1. Two sides are equal in length. 2. The angles opposite the equal sides are equal. 3. The altitude from the vertex angle bisects the base.

Front

How do you find the base angles of an isosceles triangle?

Back

To find the base angles, subtract the vertex angle from 180 degrees and then divide by 2.

Front

If the vertex angle of an isosceles triangle is 50 degrees, what are the base angles?

Back

Each base angle is 65 degrees.

Front

What is the formula for the sum of angles in a triangle?

Back

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

Front

In an isosceles triangle, if one base angle is 40 degrees, what is the vertex angle?

Back

The vertex angle is 100 degrees.

Front

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

Back

The angles opposite the equal sides are equal, and the side opposite the largest angle is the longest side.

Front

If the lengths of the two equal sides of an isosceles triangle are 5 cm, what is the minimum length of the base?

Back

The minimum length of the base must be greater than 0 cm and less than 10 cm.

Front

What is the formula for the area of an isosceles triangle?

Back

Area = (base * height) / 2.

Front

If the base of an isosceles triangle is 8 cm and the height is 5 cm, what is the area?

Back

The area is 20 cm².