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Learn how to prove triangles congruent using SSS, SAS, ASA, AAS, and HL methods. Examples and practice questions included for understanding.
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5.5 ESSENTIAL QUESTION • How do you show and use corresponding parts of congruent triangles are congruent (CPCTC) to prove triangles congruent?
Ways to Prove Triangles Congruent • SSS • SAS • ASA • AAS & if Right Triangles, then • HL
Ways to Prove Triangles Congruent • SSS • SAS • ASA • AAS & if Right Triangles, then • HL How many Parts do we NEED????
Ways to Prove Triangles Congruent • SSS • SAS • ASA • AAS & if Right Triangles, then • HL How many Parts do we NEED???? 3 2
Example 1 In the diagram, AB and CD bisect each other at M. Prove that A B. Use Corresponding Parts
Example 1 Statements Reasons 1. AB and CD bisect each other at M. 2. MA MB 2. Definition of segment bisector 3. AMD BMC 3. Vertical Angles Theorem 4. MD MC 4. Definition of segment bisector 5. ∆ADM ∆BCM 5. SAS Congruence Postulate 6. A B 6. Corresponding parts of congruent triangles are congruent. Use Corresponding Parts 1. Given
Example 2 PRACTICE: I do…. Tell what theorem or postulate you can use to show∆JGH ∆KHG. SOLUTION 1. Visualize Overlapping Triangles MarkGJH HKG andJHG KGH. Sketch the overlapping triangles separately.
Example 2 Add congruence marks to GHin each triangle. 3. You can use the AAS Congruence Theorem to show that∆JGH ∆KHG. Visualize Overlapping Triangles 2. Mark all congruent parts!
Example 3 Write a proof that shows ABDE. ABC DEC CB CE AB DE 1. Sketch the triangles separately. Use Overlapping Triangles We Do…. SOLUTION Mark all congruent parts!
Example 3 1. Given Statements Reasons 1. ABCDEC 2. CB CE 2. Given 3. C C 3. Reflexive Prop. of Congruence 4. ∆ABC∆DEC 4. ASA Congruence Postulate 5. AB DE 5. Corresponding parts of congruent triangles are congruent. Use Overlapping Triangles Show∆ABC∆DEC to prove thatABDE.
Checkpoint 1. Tell which triangle congruence theorem or postulate you would use to show that ABCD. SAS. ANSWER Use Overlapping Triangles More Practice: You do….
Checkpoint 2. Prove and show that the triangles or corresponding parts are congruent. GivenKJ KLandJ L, showNJML. Use Overlapping Triangles
Checkpoint 1. Given ANSWER 2. Given Statements Reasons 1. KJKL 2. J L 3. K K 3. Reflexive Prop. of Congruence 4. ∆KJN∆KLM 4. ASA Congruence Postulate 5. NJ ML 5. Corresponding parts of triangles are . Use Overlapping Triangles
Checkpoint 3. Given SPR QRPand Q S, Prove & show: ∆PQR ∆RSP. Use Overlapping Triangles
Checkpoint 1. Given 2. Given ANSWER Statements Reasons 1. SPRQRP 2. Q S 3. PR RP 3. Reflexive Prop. of Congruence 4. ∆PQR∆RSP 4. AAS Congruence Theorem Use Overlapping Triangles
Determine whether you can use the HL Congruence Theorem to show that the triangles are congruent. Explain your reasoning. 1. 2. ANSWER ANSWER Yes; HL Congruence Theorem can be used. No; there is no information
3. ANSWER Emile could show that the guy wires have equal length Emile and his team have erected this cellphone tower and supporting guy wires. Explain how he could use the HL Congruence Theorem to show that the guy wires are attached to the ground at equal distances from the base of the tower.