Geometry · Triangles & Congruence
Isosceles Triangle
HSG-CO.C.10
Definition
A triangle with at least two congruent sides and two congruent base angles.
Examples
- A triangle with two 7-unit sides and a 5-unit base is isosceles.
- The two base angles across from the equal sides are always congruent.
Key rule
An isosceles triangle's base angles are always congruent.
Memory hook
At least two sides match, and so do the base angles.