Question

Which of the following is not always true?

1.vertical angles are congruent 2.alternate interior angles are congruent
3.all right angles are congruent
4.all obtuse angles are congruent

Answer 1

All obtuse angles are congruent ⇒ False

Explanation:

Vertical angles and alternate interior angles are always congruent. All right angles, by definition, are equal to 90 degrees and therefore must be congruent. Obtuse angles are angles between 90 and 180 degrees. Therefore, not all obtuse angles are congruent.

Example: 127° and 163° are both obtuse but clearly not congruent.

⇒Answer choice 4