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G.CO.8 Explain how the criteria for triangle congruence (ASA, SAS, and SSS) follow from the definition of congruence in terms of rigid motions.
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G.CO.8 Explain how the criteria for triangle congruence (ASA, SAS, and SSS) follow from the definition of congruence in terms of rigid motions. Objective: Students will investigate the Side-Side-Side (SSS) and Side-Angle-Side (SAS) Triangle Congruence Theorems to prove that two triangles are congruent and draw conclusions about the angle measures of the triangles
Side-Side-Side (SSS) Congruent Postulate If 3 sides of one Triangle (Δ)are congruent ()to 3 sides of another triangle (Δ), then the triangles (Δs) are congruent ().
A Meaning: ___ ___ ___ If AB ED, AC EF & BC DF, then ΔABC ΔEDF. ___ B C ___ ___ E ___ ___ ___ ___ ___ ___ D F
Write the congruence statements for the two triangles then decide if the triangles are congruent.
Ex 2: Write the congruence statements then decide if the two triangles are congruent.SSS U Q 10 10 R S T
Ex 3: Write the congruence statements and then decide if the triangles are congruent SSS Y A X Z
You try (whiteboards)Write the congruence statements and then decide if the triangles are congruentSSS A Y X Z B C
You try (whiteboards)Write the congruence statements and then decide if the triangles are congruentSSS Y A X Z
Side-Angle-Side (SAS) If 2 sides and the included angle ()of one Δ are to 2 sides and the included angle ()of another Δ, then the 2 Δs are .
Meaning: If BC YX, ACZX, and CX, then ΔABC ΔZXY. Y B ) ( C A X Z
Ex 1:Write the congruence statements and decide if the triangles are congruent. SAS W Z X Y V
Write the congruent statements for the two triangles then decide if the triangles are congruent. Yes SAS
Example 3: Given: DE≅EB, CE ≅ EA (Mark the congruent sides) Decide if the triangles are congruent. YES SAS B A C E D
You try: Whiteboards Write the congruence statements and decide if the triangles are congruent.
Write the congruence statements and decide if the triangles are congruent. SSS S Q R T
Write the congruence statements and decide if the triangles are congruent. SAS D A G R
Given: SD≅TC, CS≅DT Prove: ΔCST ≅ ΔDTS SSS ST =ST reflexive property D C K S T
Ex. 2: • Given: A is the midpoint of MT, A is the midpoint of SR. • Prove the triangles are congruent MA = AT def of midpoint SA = RA <A =<A Vertical angles
ASA QR = RS def of midpoint