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 two angles that are equal.

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 two angles of a triangle are equal, what type of triangle is it?

Back

It is an isosceles triangle.

Front

What is the vertex angle in an isosceles triangle?

Back

The vertex angle is the angle opposite the base of the isosceles triangle.

Front

How do you find the vertex angle if the base angles are known?

Back

The vertex angle can be found using the formula: Vertex Angle = 180° - 2(Base Angle).

Front

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

Back

The vertex angle is 100°.

Front

What is the base of an isosceles triangle?

Back

The base is the side that is not equal in length to the other two sides.

Front

In an isosceles triangle, how do you determine the length of the equal sides if the base is known?

Back

You can use the Pythagorean theorem if the height is known, or apply the properties of isosceles triangles.

Front

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

Back

The angles opposite the equal sides are also equal.

Front

How do you calculate the missing angle in an isosceles triangle?

Back

Subtract the sum of the known angles from 180°.