What type of triangle is characterized by having one angle greater than 90 degrees?

A triangle with one angle greater than 90 degrees is classified as an obtuse triangle. This characteristic is essential as it distinguishes obtuse triangles from other types. Specifically, in an obtuse triangle, the presence of the obtuse angle (greater than 90 degrees but less than 180 degrees) means that the other two angles must be acute, ensuring their measures are each less than 90 degrees and together complement the obtuse angle to total 180 degrees for the triangle.

In contrast, a right triangle contains one angle exactly equal to 90 degrees, while an acute triangle consists exclusively of three angles that are each less than 90 degrees. An equilateral triangle, on the other hand, has all three sides and angles equal, with each angle measuring exactly 60 degrees, thereby never exceeding 90 degrees. Therefore, the defining characteristic of having one angle greater than 90 degrees clearly identifies the triangle as obtuse.