Question

if triangle def has a 90° angle at vertex e, which statements are true? select two options. triangle def is an obtuse triangle. the angle at vertex d is acute. the angle at vertex f is obtuse. triangle def is a right triangle. the angle at vertex d is obtuse.

Explanation:

Step1: Identify triangle type

A triangle with a 90° angle is a right triangle. So "Triangle DEF is a right triangle" is true.

Step2: Check other angles

Sum of angles in a triangle is 180°. Since ∠E=90°, ∠D+∠F=90°, so both ∠D and ∠F are acute. Thus "The angle at vertex D is acute" is true.

Answer:

The angle at vertex D is acute, Triangle DEF is a right triangle