Question

Triangle ABC is an obtuse triangle with the obtuse angle at vertex B. Angle A must be

less than 90°.
greater than 90°.
congruent to angle B.
congruent to angle C

Answer 1

"less than 90°."

Explanation:

This is because an obtuse triangle can be defined as "An obtuse triangle (or obtuse-angled triangle) is a triangle with one obtuse angle (greater than 90°) and two acute angles." Therefore, there can only be ONE obtuse angle. Therefore, with the obtuse angle being at vertex B, there cannot be another one at vertex A.