Triangle Theorems (5/30 Plus)

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 degrees.

Front

What is the Triangle Inequality Theorem?

Back

The Triangle Inequality Theorem states that the sum of the lengths of any two sides of a triangle must be greater than the length of the third side.

Front

If one angle of a triangle is 90 degrees, what type of triangle is it?

Back

It is a right triangle.

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 degrees.

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 a scalene triangle?

Back

A scalene triangle is a triangle in which all three sides are of different lengths and all three angles are different.

Front

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

Back

To find an unknown angle, subtract the sum of the known angles from 180 degrees.

Front

What is the exterior angle theorem?

Back

The exterior angle theorem states that the measure of an exterior angle of a triangle is equal to the sum of the measures of the two opposite interior angles.

Front

If two angles of a triangle are 45 degrees and 55 degrees, what is the third angle?

Back

The third angle is 80 degrees (180 - 45 - 55 = 80).

Front

What is the relationship between the sides and angles of a triangle?

Back

In a triangle, the larger the angle, the longer the opposite side.