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4.3  Δ s

4.3  Δ s. Objectives. Name and label corresponding parts of congruent triangles Identify congruence transformations.  Δ s. Triangles that are the same shape and size are congruent. Each triangle has three sides and three angles.

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4.3  Δ s

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  1. 4.3 Δs

  2. Objectives • Name and label corresponding parts of congruent triangles • Identify congruence transformations

  3. Δs • Triangles that are the same shape and size are congruent. • Each triangle has three sides and three angles. • If all six of the corresponding parts are congruent then the triangles are congruent.

  4. CPCTC • CPCTC – Corresponding Parts of Congruent Triangles are Congruent • Be sure to label Δs with proper mappings (i.e. if D  L, V  P, W  M, DV  LP, VW  PM, and WD  ML then we must write ΔDVW ΔLPM)

  5. Congruence Transformations • Congruency amongst triangles does not change when you… • slide, • turn, • or flip • … one of the triangles.

  6. So, we can only prove Δs  if ALL sides AND ALL s are . NO! • There are some shortcuts…

  7. 4.3 Proving Δs are  : SSS and SAS

  8. Objectives • Use the SSS Postulate • Use the SAS Postulate

  9. Postulate 4.1 (SSS)Side-Side-Side  Postulate • If 3 sides of one Δ are  to 3 sides of another Δ, then the Δs are .

  10. A SSS Postulate ___ ___ ___ ___ If seg AB  seg ED, seg AC  seg EF, & seg BC  seg DF, then ΔABC ΔEDF. B C ___ ___ E ___ ___ ___ ___ ___ ___ D F

  11. Given: QR  UT, RS  TS, QS=10, US=10Prove: ΔQRS ΔUTS U Q 10 10 R S T

  12. Proof Statements Reasons 1. QR  UT, RS  TS,1. Given QS=10, US=10 2. QS=US 2. Substitution 3. QS  US 3. Def of  segs. 4. Δ QRS Δ UTS 4. SSS Postulate

  13. Postulate 4.2 (SAS)Side-Angle-Side  Postulate • If 2 sides and the included  of one Δ are  to 2 sides and the included  of another Δ, then the 2 Δs are .

  14. SAS Postulate • If seg BC  seg YX, seg AC  seg ZX, & C X, then ΔABC  ΔZXY. B Y ) ( C A X Z

  15. Given: WX  XY, VX  ZX Prove: Δ VXW Δ ZXY W Z X 1 2 Y V

  16. Proof Statements Reasons 1. WX  XY; VX  ZX 1. Given 2. 1 2 2. Vert s Thm. 3. Δ VXW Δ ZXY 3. SAS Postulate

  17. Given: RS  RQ and ST  QTProve: Δ QRT  Δ SRT. S Q R T

  18. Proof Statements Reasons 1. RS  RQ; ST  QT 1. Given 2. RT  RT 2. Reflexive 3. Δ QRT Δ SRT 3. SSS Postulate

  19. Given: DR  AG and AR  GRProve: Δ DRA  Δ DRG. D R A G

  20. Statements 1. DR  AG; AR  GR 2. DR  DR 3.DRG & DRA are rt. s 4.DRG   DRA 5. Δ DRG  Δ DRA Reasons 1. Given 2. Reflexive Property 3.  lines form 4 rt. s 4. Right s Theorem 5. SAS Postuate Proof

  21. Assignment Pre-AP: Pg. 195 #9 – 16, 22 – 25 Pg. 204 #14 – 19, 22 – 25

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