The Compendium Geometry is an eBook providing facts, formulas and explanations about geometry.

Isosceles Triangle

If two sides of a triangle (a and b in the figure at the left) are equal but different to the third side, this triangle is called an isosceles triangle. This property is equivalent to two angles of the triangle being equal. The name is derived from the Greek iso (same) and skelos (leg).

The following table shows the most important properties of an isosceles triangle:

Property Formula
Height hc
Height ha, hb ha = hb = chc/a
Length of the median
Radius of the incircle
Radius of the circumcircle

Last Update: 2010-12-06