Proof Using ASA and AAS
Pacing:This lesson should take one class period
Goal:Students will learn how triangles can be determined congruent using Angle-Side-Angle and Angle-Angle-Side
Theorems.
Look out!These two congruency postulates look identical to students. Use this method when explaining which to
use. Whenmoving left to right of a triangle,recite the information you have. If you have an angle-angle-side (or
side-angle-angle), use the AAS Congruence Theorem. If you have an angle-side-angle, use the ASA Congruence
Postulate.In-class activity:Have the students complete the following two activities:
Activity #1: Have students draw a 42 degree angle. Measure one ray 5 cm. Using the unmeasured ray, students will
now draw a 70 degree angle. Connect both rays to form a triangle. Have students share their drawings.All drawings
should be congruent, according to AAS.
Activity #2: Have students draw a 55 degree angle, measuring one ray 5 cm.Using this same ray, construct a second
angle of measure of 85 degrees.Connect both rays to form a triangle. Have students share their drawings(all
drawings should be congruent, according to ASA).
Chapter 1. Geometry TE - Teaching Tips