The Isosceles Triangle Theorem states: If two sides of a triangle are congruent, then angles opposite those sides are congruent.

What are the 5 theorems of a triangle?

AAS (angle, angle, side)

If two angles and the non-included side of one triangle are equal to the corresponding angles and side of another triangle, the triangles are congruent.

What is AAA theorem?

Euclidean geometry

may be reformulated as the AAA (angle-angle-angle) similarity theorem: two triangles have their corresponding angles equal if and only if their corresponding sides are proportional.