Explanation:
A triangle has 3 angles.
The sum of the measures of the three angles is 180°.
A right triangle has one right angle.
A right angle measures 90°.
What total number of degrees is left for the other two angles?
180° - 90° = 90°
The two other angles of a right triangle have measures that add up to 90°.
That means each one of them must measure less than 90°.
Since the right angle measures 90°, and each of the other 2 angles measures less than 90°, the right angle has the greatest measure. This means the other two angles are acute angles.