Question

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

Answer 1

Answer:

Angle A must be acute.

Explanation:

Both angle A and C must be acute. The sum of the angles in a triangle is 180°.

An obtuse angle is more than 90°, so the sum of the remaining 2 angles has to be less than 90°.

Note that it is impossible to have:

2 right angles in a triangle, because 90°+90°=180° and the third angle still needs to be added.1 obtuse and 1 right angle in a triangle, their sum is more than 180°2 obtuse angles in a triangle, their sum is more than 180°

It is possible to have an obtuse-angled isosceles triangle, but the vertex angle must be obtuse and the equal base angles will be acute.