Question

Which biconditional statement below is true?

Angles are congruent if and only if they are vertical angles.
Angles are congruent if and only if they are vertical angles.

Angles are supplementary if and only if their sum is 180°.
Angles are supplementary if and , only if their sum is 180°.

A number is a whole number if and only if it is a natural number.
A number is a whole number if and only if it is a natural number.

Points are collinear if and only if they are coplanar.
Points are collinear if and only if they are coplanar.

Answer 1

Answer: Angles are supplementary if and only if their sum is 180° is true.

Explanation:

Test by making both parts negative: Angles are not supplementary if and only if their sum is not 180° This is also true.