California Assessment of Student Performance and Progress (CAASPP) Math Practice Exam 2025 - Free CAASPP Math Practice Questions and Study Guide.

A right triangle is defined by the presence of one angle that measures exactly 90 degrees. This characteristic is fundamental to its classification and distinguishes it from other types of triangles. The right angle is the cornerstone of various properties and theorems, such as the Pythagorean theorem, which relates the lengths of the sides in a right triangle.

The other characteristics mentioned do not apply to right triangles. A triangle with all sides equal in length corresponds to an equilateral triangle, and a triangle with one angle greater than 90 degrees is classified as an obtuse triangle. Additionally, the statement that a right triangle is always isosceles implies the triangle has at least two equal sides, which is not a requisite for right triangles, as they can also have sides of all different lengths. Hence, the defining property of a right triangle is its right angle.