Task# Similar Triangles I

Illustrative MathematicsVaries

The goal of this task is to prepare students for the angle-angle criterion for triangle similarity. Since the sum of the three angles in a triangle is always 180 degrees, having two pairs of congruent corresponding angles in two triangles tells us that the third pair of corresponding angles is also congruent. For this reason, the AAA criterion for similarity which is presented in this task is often simplified to the AA criterion for similarity. But establishing the fact that the sum of the interior angles in a triangle is 180 degrees also belongs in the eighth grade, under the same 8.G.A.5 standard.