Triangle Sum Theorem

Front

What is the Triangle Sum Theorem?

Back

The Triangle Sum Theorem states that the sum of the interior angles of a triangle is always 180°.

Front

If one angle of a triangle is 90° and another is 50°, what is the measure of the third angle?

Back

The third angle is 40° (90° + 50° + ? = 180°).

Front

What is the measure of angle DFE if 43° + 84° + ? = 180°?

Back

53°.

Front

What is the missing angle if ? + 52° + 87° = 180°?

Back

41°.

Front

What is the missing angle if ? + 90° + 50° = 180°?

Back

40°.

Front

Which set of angles would NOT make a triangle? 30°, 70°, 80°; 40°, 30°, 110°; 80°, 20°, 60°; 50°, 60°, 70°?

Back

80°, 20°, and 60° (80° + 20° + 60° = 160° < 180°).

Front

What is a triangle?

Back

A triangle is a polygon with three edges and three vertices.

Front

What are the types of triangles based on angles?

Back

Triangles can be classified as acute (all angles < 90°), right (one angle = 90°), or obtuse (one angle > 90°).

Front

What is an acute triangle?

Back

An acute triangle is a triangle where all three angles are less than 90°.

Front

What is a right triangle?

Back

A right triangle is a triangle that has one angle equal to 90°.