Which triangle has one angle that measures 90 degrees?

A triangle that has one angle measuring 90 degrees is known as a right triangle. This specific type of triangle is defined by having one of its angles as a right angle, which is an angle that exactly measures 90 degrees. Right triangles have essential properties, including the Pythagorean theorem, which relates the lengths of the sides of the triangle: the sum of the squares of the lengths of the two legs (the sides forming the right angle) equals the square of the length of the hypotenuse (the side opposite the right angle).

In terms of the other types of triangles mentioned: an isosceles triangle has two sides of equal length and consequently two equal angles, but it does not necessarily contain a right angle. A scalene triangle has all sides and all angles of different measures, which also means it does not guarantee the presence of a right angle. An equilateral triangle, with all three sides and angles equal (each measuring 60 degrees), cannot have a right angle either. Thus, the defining feature of a right triangle is the presence of that 90-degree angle, distinguishing it clearly from all other types of triangles.