Flashcard 14 - Mathematics: Geometric and Spatial Reasoning Flashcard Set for the TSIA2

obtuse triangle

In classifying triangles by angles, we can have three types of triangles: acute, obtuse, and right triangles.

An acute triangle is a triangle where all three of its angles are acute (less than \(90^{\circ}\).

An obtuse triangle is a triangle where one of its angles is obtuse (greater than \(90^{\circ}\) but less than \(180^{\circ}\).

A right triangle is a triangle in which one angle is a right angle (\(=90^{\circ}\)).

The triangle shown has one angle that is greater than 90 degrees but less than 180 degrees. It is the \(130^{\circ}\) angle. Hence, this triangle is an obtuse triangle.