Defining Triangles

A triangle is a three sided shape that is classified by either the angle measures or the side-lengths. Triangles classified under angle measures consist of four different types: Acute, Equiangular, Right, and Obtuse. To know what a triangle is classified as a specific angle measurement triangle, look at each angle. If the triangle has three angles that are less than 90 degrees, then that means it is an acute triangle. An equiangular triangle is when all three angles in the triangle are congruent and acute. If it is a right triangle, that means that there must be one angle that is equal to 90 degrees. Lastly, to tell if a triangle is obtuse, there must be one angle that is larger than 90 degrees.

Next, triangles can be classified as in side-lengths. There are three different types of side-length triangles: Equilateral, Isosceles, and Scalene. As shown in the picture below, each side-length triangle represents a different number of congruent sides. Equilateral Triangles have three congruent sides. An Isosceles Triangle has two congruent sides. Lastly, a Scalene Triangle has no congruent sides.