Isosceles Triangle Theorem

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 the Isosceles Triangle Theorem?

Back

The Isosceles Triangle Theorem states that in an isosceles triangle, the angles opposite the equal sides are equal.

Front

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

Back

The sides opposite the equal angles are also equal in length.

Front

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

Back

The base angles will each measure 70° because the sum of angles in a triangle is 180°.

Front

How do you find the value of x in an isosceles triangle when given the lengths of the sides in terms of x?

Back

Set the lengths of the two equal sides equal to each other and solve for x.

Front

If the lengths of the equal sides of an isosceles triangle are represented as 3x - 2 and 2x + 1, how do you find x?

Back

Set 3x - 2 = 2x + 1 and solve for x.

Front

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

Back

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

Front

If the vertex angle of an isosceles triangle is 60°, what are the measures of the base angles?

Back

The base angles will each measure 60° because the sum of angles in a triangle is 180°.

Front

In triangle LMN, if LM = LN, what can be inferred about angles L and N?

Back

Angles L and N are equal because they are opposite the equal sides.

Front

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

Back

In an isosceles triangle, equal sides correspond to equal angles.