Question

m∠3 + m∠2 + m∠1 = 180°
a triangles angles sum to 180°.

Explanation:

The problem is about the sum of the interior angles of a triangle. The formula given is \( m\angle3 + m\angle2 + m\angle1 = 180^\circ \), which is the Triangle Angle Sum Theorem. This theorem states that the sum of the measures of the interior angles of a triangle is always \( 180^\circ \).

Answer:

The missing term is "interior". So the complete statement is: "A triangle’s interior angles sum to \( 180^\circ \)."