What are three ways to classify a triangles by its angles?

The three kinds of triangles are:

right triangle :one of the angles is a right angle (i.e. measures 90 degrees)

acute: All of the angles measures less than 90 degrees. A special case of acute is

the equiangular or equilateral triangle in which all angles measure 60 degrees;

obtuse: One of the angles measure more than 90 degrees.