Lesson: Congruence of Triangles: ASA and AAS Mathematics • 8th Grade

In this lesson, we will learn how to prove that two triangles are congruent using either the angle-side-angle (ASA) or the angle-angle-side (AAS) criterion and determine whether angle-side-side is a valid criterion for triangle congruence or not.

Lesson Plan

Students will be able to

recognize whether two given triangles are congruent,
recognize that ASA and AAS are conditions of congruency but that SSA is not,
recognize whether ASA or AAS can be used to prove that two given triangles are congruent,
solve a word problem or a more complex geometric problem using ASA or AAS.

Lesson Video

Lesson Worksheet

Q1:

Determine the lengths of and .

Q2:

The two triangles in the given figure share the measures of two angles and the length of one side. Does a rigid transformation exist that would map triangle to triangle , and, hence, are the two triangles congruent?

Q3:

Two triangles contain angles of equal measures.

Can we prove that the triangles are similar?

Can we prove that the two triangles are congruent?