Interior and Exterior Angles of Triangles

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

Back

It is a right triangle.

Front

What is an exterior angle of a triangle?

Back

An exterior angle is formed by one side of the triangle and the extension of an adjacent side.

Front

How do you calculate the measure of an exterior angle?

Back

The measure of an exterior angle is equal to the sum of the two opposite interior angles.

Front

If two angles of a triangle are 50° and 60°, what is the measure of the third angle?

Back

The third angle measures 70° (180° - 50° - 60°).

Front

What is the relationship between the interior and exterior angles of a triangle?

Back

The exterior angle is equal to the sum of the two non-adjacent interior angles.

Front

What is the measure of each angle in an equilateral triangle?

Back

Each angle in an equilateral triangle measures 60°.

Front

If one angle of a triangle is 110°, what can you say about the other two angles?

Back

The other two angles must be acute (less than 90°) because the sum must equal 180°.

Front

What is the formula to find the missing angle in a triangle?

Back

The formula is: Missing angle = 180° - (sum of the known angles).

Front

In a triangle, if one angle is twice the size of another, what is the relationship between the angles?

Back

Let the smaller angle be x; then the larger angle is 2x. The equation is x + 2x + third angle = 180°.