Isosceles and Equilateral Triangles

Isosceles triangles are triangles with two sides of equal length. Therefore if we know the measure of one angle we can calculate the measure of the remaining angles. If we know that the measure of the unequal angle is 30 degrees we can deduce that the remaining angles must each equal 75 degrees.

Let x equal the measure of our two equal angles. This 2x + 30 must equal 180, or the total measure of degrees in a triangle.

2x + 30 = 180
2x=150
x=75


Equilateral triangles are triangles which have sides of equal length and therefore angles of equal length. The angles of an equilateral triangle will always equal 60 degrees or (pi)/3 radians.