Question

One angle in an obtuse isosceles triangle measures 40°. What are the measures of the other two angles?

70° and 70°
80° and 80°
40° and 100°
40° and 120°

Answer 1

40° and 100°

Explanation:

Answer 2

An obtuse triangle has one obtuse angle, or an angle that measures more than 90° but less than 180°. Options 1 and 2 are not correct, because these are acute angles.
So, one of the angles must be 40°, and the other may be 100° or 120°.
The measures of the angles in a triangle add up to 180°.

`40^\circ + 40^\circ +x = 180^\circ \\ 80^\circ + x=180^\circ \\ x=180^\circ - 80^\circ \\ x=100^\circ`
The other two angles are 40° and 100°.