FTCE General Knowledge Math Practice Test

What is a triangle called that includes one obtuse angle?

1. Equilateral Triangle

2. Scalene Triangle

3. Acute Triangle

4. Obtuse Triangle

The correct answer is: Obtuse Triangle

A triangle that has one obtuse angle is classified as an obtuse triangle. An obtuse angle is defined as an angle greater than 90 degrees but less than 180 degrees. In this type of triangle, the presence of the obtuse angle means that the other two angles must be acute, as the sum of all angles in a triangle is always 180 degrees. This characteristic differentiates it from other types of triangles, such as equilateral triangles, where all angles are equal (and acute), or scalene triangles, which may have all angles acute or one right angle but cannot have an obtuse angle. Acute triangles consist entirely of angles less than 90 degrees, making them distinctly different from obtuse triangles. Thus, an obtuse triangle is the correct classification for a triangle with one angle measuring greater than 90 degrees.