The Isosceles Triangle

Mathematics — Second Preparatory

Properties of an isosceles triangle

Comparison aspect	Main idea	Keywords
First property	the two base angles are equal	baseanglesequal
Second property	the altitude drawn from the vertex to the base bisects the base and bisects the vertex angle	altitudedrawnvertexbase
Converse	if two angles of a triangle are equal the sides opposite them are equal and the triangle is isosceles	anglestriangleequalsides
•	Since the angles of a triangle add up to 180° if we know the vertex angle we can find each base angle: base angle = (180° − vertex angle) ÷ 2	Sinceanglestriangleknow

The Isosceles Triangle · 2 / 5