How to prove similar triangles<br>Define the angle-angle (aa) theorem. Two triangles can be proved similar by the angle-angle theorem which states: if two triangles have two congruent angles, then those triangles are similar. [substeps] This theorem is also called the angle-angle-angle (aaa) theorem because if two angles of the triangle are congruent, the third angle must also be congruent.
triangles were drawn by arnold