4-2 Isosceles Triangle Theorem

Front

What is the Isosceles Triangle Theorem?

Back

In an isosceles triangle, the angles opposite the equal sides are equal.

Front

If two sides of a triangle are equal, what can be said about the angles opposite those sides?

Back

The angles opposite the equal sides are also equal.

Front

Sketch an isosceles triangle and label the equal sides and angles.

Back

An isosceles triangle with sides AB = AC and angles ∠B = ∠C.

Front

What is the sum of the angles in any triangle?

Back

The sum of the angles in any triangle is 180 degrees.

Front

If one angle of an isosceles triangle is 40 degrees, what are the measures of the other two angles?

Back

The other two angles are each 70 degrees.

Front

In an isosceles triangle, if the equal sides are 10 cm each, what is the minimum possible length of the base?

Back

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

Front

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

Back

The base angles are each 65 degrees.

Front

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

Back

Subtract the known angle from 180 degrees and divide by 2.

Front

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

Back

The longer side is opposite the larger angle.

Front

If the base angles of an isosceles triangle are 30 degrees, what is the vertex angle?

Back

The vertex angle is 120 degrees.