5-6 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 and the angles opposite those sides are 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

In an equilateral triangle, what is the measure of each angle?

Back

Each angle in an equilateral triangle measures 60°.

Front

If two angles of an isosceles triangle are 76°, what is the measure of the vertex angle?

Back

The vertex angle measures 28°.

Front

What is the base of an isosceles triangle?

Back

The base of an isosceles triangle is the side that is not equal in length to the other two sides.

Front

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

Back

The maximum possible length of the base is less than 20 cm.

Front

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

Back

The angles opposite the equal sides are equal.

Front

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

Back

The sum of the angles in a triangle is always 180°. Subtract the sum of the known angles from 180° to find the unknown angle.

Front

If ∠B and ∠C are equal in an isosceles triangle, what can we conclude about the triangle?

Back

The triangle is isosceles.

Front

What is the formula for the area of a triangle?

Back

The area of a triangle is given by the formula: Area = 1/2 * base * height.