If the sum of two angles in a triangle is 90 degrees, what type of triangle is it?

When the sum of two angles in a triangle is 90 degrees, it implies that the remaining angle must be 90 degrees as well. This situation satisfies the definition of a right triangle, which is characterized by having one angle that measures exactly 90 degrees. In any triangle, the total sum of the angles must equal 180 degrees. Therefore, if you have two angles summing to 90 degrees, the third angle must also complete the total of 180 degrees, resulting in that angle being a right angle.

In contrast, an acute triangle is one where all angles are less than 90 degrees, while an obtuse triangle contains one angle that is greater than 90 degrees. An equilateral triangle has all three angles equal to 60 degrees, which does not meet the condition of two angles summing to 90 degrees. Thus, the described triangle is definitively a right triangle due to the presence of the 90-degree angle.