Week 4 Warm Up 11.07.11 Tell whether each statement is needed to show congruence: 1) The figures must have the same size. 2) The figures must be polygons. Add theorem 2.1 here next year. 3) The figures must have the same shape.

SSS - Side Side Side Congruence Geometry 4.3 Day 1 I will prove that triangles are congruent using the SSS and SAS Postulates. Postulate 19 SSS - Side Side Side Congruence If three sides of one triangle are congruent to three sides of a second triangle, then the two triangles are congruent. P M N S Q R ≅ ≅ ≅ ∆MNP ≅ ∆QRS because of SSS.

Ex 1 Prove ∆PQW ≅ ∆TSW: P W S T Q ≅ ≅ , ≅ , because they are given. ∆PQW ≅ ∆TSW because of SSS.

SAS - Side Angle Side Congruence Postulate 20 SAS - Side Angle Side Congruence If two sides and the included angle of one triangle are congruent to two sides and the included angle of a second triangle, then the two triangles are congruent. P Q S W X Y ≅ ∠Q ≅ ∠X ≅ ∆PQS ≅ ∆WXY because of SAS.

Ex 2 Prove ∆ABE ≅ ∆DCE: Statements Reasons ≅ , ∠1 ≅ ∠2 ∆AEB ≅ ∆DEC   ≅ , Given ∠1 ≅ ∠2 Vertical Angle Theorem ∆AEB ≅ ∆DEC SAS Congruence Postulate

because of the reflexive property of congruence. Prove ∆PQR ≅ ∆PSR: P S R Q ≅ they are given. 1) ≅ 2) ≅ because of the reflexive property of congruence. 3) ∆PQR ≅ ∆PSR because of SSS.

Is ∆PQR ≅ ∆SRQ? Give 3 congruency statement to prove it? Do: 1 Is ∆PQR ≅ ∆SRQ? Give 3 congruency statement to prove it? P Q S R Add theorem 2.1 here next year. Assignment: Textbook Page 216, 3 - 17 all.