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 is the vertex angle in an isosceles triangle?

Back

The vertex angle is the angle formed by the two equal sides of an isosceles triangle.

Front

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

Back

The vertex angle is 100°.

Front

In a right isosceles triangle, what is the measure of the angles?

Back

In a right isosceles triangle, one angle is 90° and the other two angles are each 45°.

Front

How do you find the length of the equal sides in an isosceles triangle given the base?

Back

Use the Pythagorean theorem or properties of isosceles triangles to find the lengths.

Front

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

Back

The angles opposite the equal sides are equal.

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 less than 10 cm (the sum of the lengths of the two equal sides).

Front

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

Back

Area = (base * height) / 2.

Front

If DE = x + 7, DF = 3x - 1, and EF = 2x + 5 in triangle DEF, how do you find x?

Back

Set DE = DF and solve for x: x + 7 = 3x - 1.

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°.