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à 3.3èCongruent Triangles
äèPlease prove that ê followïg pairs ç triangles are
congruent or show that êy are not congruent.
â
èèèèèè Two triangles are congruent if å only if all
èèèèèè pairs ç correspondïg parts are congruent.
éS1èèèèèèèèèèèèèèèè Two triangles are congruent if
èèèèèèèèèèèèèèèèèèèè êy have ê same size å
èèèèèèèèèèèèèèèèèèèè shape.èA test for congruence
èèèèèèèèèèèèèèèèèèèè could be ë rotate one triangle
èèèèèèèèèèèèèèèèèèèè or flip å rotate one triangle
@fig3301.BMP,35,30,147,74èèèèèèèèover ê oêr triangle ë seeèèèèèèèèèèèè
if êy match up perfectly.èIf êy do, ên êy are congruent.
è The equal parts ç congruent triangles are called correspondïg parts.
For example, ï ê above figure ▒╖ å ╜└ are correspondïg parts.è
Also, ╬A corresponds ë ╬H.èWhen two triangles are congruent, we can
say ΦABC ╧ ΦHEP.èNotice that ê order ç ê letters matches ê cor-
respondïg angles.èNotice also ï ê figure that correspondïg parts
have ê same marks.
Defïition 3.3.1èCONGRUENT TRIANGLES:èTwo triangles are congruent if
all ê pairs ç correspondïg parts are congruent.
èèIt will not be necessary ï a proç ë show that all six pairs ç
correspondïg parts are congruent.èThe followïg three axioms allow
us ë show triangles are congruent by provïg three pairs ç parts are
congruent.
Axiom 16:èIf two angles å ê ïcluded side ç one triangle are con-
gruent ë ê correspondïg parts ç anoêr triangle, ên ê tri-
angles are congruent.
Axiom 17:èIf two sides å ê ïcluded angle ç one triangle are con-
gruent ë ê correspondïg parts ç anoêr triangle, ên ê tri-
angles are congruent.
Axiom 18:èIf three sides ç one triangle are congruent ë ê corres-
pondïg sides ç anoêr triangle, ên ê triangles are congruent.
èèèèèè
èèèèèèèèèèèèèèèèIn ê figure you are given ïformation
èèèèèèèèèèèèèèèèabout ê two triangles.èFor example it
èèèèèèèèèèèèèèèèis seen that BC = HC å AC = EC.èIs
èèèèèèèèèèèèèèèèthis enough ïformation ë prove that
èèèèèèèèèèèèèèèèê two triangles are congruent?èTheèè
@fig3302.BMP,55,230,147,74èèèfollowïg êorem proves congruence.
èèTheorem: Show that ΦABC ╧ ΦEHC
èèèProç: Statementèèèèèèèèèè Reason
èèèèèè 1. BC = HCèèèèèèèèèè1. Given
èèèèèè 2. AC = ECèèèèèèèèèè2. Given
èèèèèè 3. m╬BCA = m╬HCEèèèèèèè3. Vertical angles
èèèèèè 4. ┤╖ ╧ ╜╖, ▒╖ ╧ ║╖èèèèè 4. Defïition ç congruence
èèèèèè 5. ╬BCA ╧ ╬HCEèèèèèèèè5. Defïition ç congruence
èèèèèè 6. ΦABC ╧ ΦEHCèèèèèèèè6. (17)Congruent by SAS
1èè Can you establish ê congruence ç ΦABC å ΦHEC?
èèèèèèèèèèèèèèèèèèèèèèèèè A) Yes
èèèèèèèèèèèèèèèèèèèèèèèèè B) No
@fig3303.BMP,35,40,147,74
üèèèèèShow ΦABC ╧ ΦHEC
èèèè Proç: StatementèèèèèèèèèèèReason
èèèèèèèè1. ╬B ╧ ╬Eèèèèèèèèèè 1. Given
èèèèèèèè2. ┤╖ ╧ ║╖èèèèèèèèèè 2. Given
èèèèèèèè3. ╬BCA ╧ ╬ECHèèèèèèèè 3. Vertical angles
èèèèèèèè4. ΦABC ╧ ΦHECèèèèèèèè 4. Congruent by ASA
Ç A
2èèèèèèèCan you establish ê congruence ç ΦABC å ΦHEC
èèèèèèèèèèèèèèèèèèèè if ▒╜ å ┤║ bisect each oêr?èèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèè A) Yes
èèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèè B) No
@fig3304.BMP,35,40,147,74
üèèèèShow ΦABC ╧ ΦHEC
èèè Proç: Statementèèèèèèèèè Reason
èèèèèèè1. ▒┤ ╧ ╜║èèèèèèèèè1. Given
èèèèèèè2. AC = CHèèèèèèèèè2. Defïition ç bisect
èèèèèèè3. BC = CEèèèèèèèèè3. Defïition ç bisect
èèèèèèè4. ▒╖ ╧ ╜╖èèèèèèèèè4. Defïition ç congruence
èèèèèèè5. ┤╖ ╧ ║╖èèèèèèèèè5. Defïition ç congruence
èèèèèèè6. ΦABC ╧ ΦHECèèèèèèè6. Congruent by SSS
Ç A
3èCan you establish ê congruence ç ΦABC å ΦEBC if AC = EC?èèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèèèA) Yesèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèèèB) No
@fig3305.BMP,35,40,147,74
üèèè Show ΦABC ╧ ΦEBC
èèèProç: Statementèèèèèèèèè Reason
èèèèèè 1. AC = ECèèèèèèèèè1. Given
èèèèèè 2. ▒╖ ╧ ║╖èèèèèèèèè2. Defïition ç congruence
èèèèèè 3. ╬ACB ╧ ╬ECBèèèèèèè3. Given
èèèèèè 4. CB = CBèèèèèèèèè4. Reflexive axiom
èèèèèè 5. ╖┤ ╧ ╖┤èèèèèèèèè5. Defïition ç congruence
èèèèèè 6. ΦABC ╧ ΦEBCèèèèèèè6. Congruent by SAS
Ç A
4è Can you establish ê congruence ç ΦABC å ΦCEA if AE = BCèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèèèèèèèå AB = EC?
èè
èèèèèèèèèèèèèèèèèèèèèèèèèè A) Yesèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèèè B) No
@fig3306.BMP,35,40,147,74
üèèèèShow ΦABC ╧ ΦCEA
èèè Proç: Statementèèèèèèèèè Reason
èèèèèèè1. AE = BC, AB = ECèèèè 1. Given
èèèèèèè2. ▒║ ╧ ╖┤, ▒│ ╧ ║╖èèèè 2. Defïition ç congruence
èèèèèèè3. AC = ACèèèèèèèèè3. Reflexive axiom
èèèèèèè4. ▒╖ ╧ ▒╖èèèèèèèèè4. Defïition ç congruence
èèèèèèè5. ΦABC ╧ ΦCEAèèèèèèè5. Congruent by SSS
Ç A
5è Can you establish ê congruence ç ΦABC å ΦEBP if AB = EBèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèèèèèèèå AP = EC?
èè
èèèèèèèèèèèèèèèèèèèèèèèèèè A) Yesèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèèè B) No
@fig3307.BMP,35,40,147,74
üèèèèShow ΦABC ╧ ΦEBP
èèè Proç: Statementèèèèèèèèè Reason
èèèèèèè1. AB = EB, AP = ECèèèè 1. Given
èèèèèèè2. ▒┤ ╧ ║┤èèèèèèèèè2. Defïition ç congruence
èèèèèèè3. m╬B = m╬Bèèèèèèèè3. Reflexive axiom
èèèèèèè4. ╬B ╧ ╬Bèèèèèèèèè4. Defïition ç congruence
èèèèèèè5. AB - AP = EB - APèèèè5. Subtrac. axiom ç equality
èèèèèèè6. AB - AP = EB - ECèèèè6. Substitution from 1
èèèèèèè7. AP+PB - AP = EC+CB - ECè7. (8)Segment addition axiomè
èèèèèèè8. PB = CBèèèèèèèèè8. Commu. å assoc. axioms
èèèèèèè9. └┤ ╧ ╖┤èèèèèèèèè9. Defïition ç congruence
èèèèèè 10. ΦABC ╧ ΦEBPèèèèèè 10. Congruent by SAS
Ç A
6è Can you establish ê congruence ç ΦAPE å ΦECA if AB = EBèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèèèèèèèå AP = EC?
èè
èèèèèèèèèèèèèèèèèèèèèèèèèè A) Yesèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèèè B) No
@fig3307.BMP,35,40,147,74
üèèèèShow ΦAPE ╧ ΦECA
èèè Proç: Statementèèèèèèèèè Reason
èèèèèèè1. AB = EB, AP = ECèèèè 1. Given
èèèèèèè2. ▒└ ╧ ║╖èèèèèèèèè2. Defïition ç congruence
èèèèèèè3. AE = AEèèèèèèèèè3. Reflexive axiom
èèèèèèè4. ▒║ ╧ ▒║èèèèèèèèè4. Defïition ç congruence
èèèèèèè5. ▒╖ ╧ ║└èèèèèèèèè5. Problem 5 å correspondïg
èèèèèèèèèèèèèèèèèèèèèèè parts ç congruent Φs
èèèèèèè6. ΦAPE ╧ ΦECAèèèèèèè6. Congruent by SSS
Ç A
7è Can you establish ê congruence ç ΦACE å ΦHCB if ╬A ╧ ╬Hèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèèèèèèèå ▒║ ╧ ╜┤?
èè
èèèèèèèèèèèèèèèèèèèèèèèèèè A) Yesèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèèè B) No
@fig3308.BMP,35,40,147,74
üèèèèèè
èèèèèèèèèèèèèèè
èèèèèèèèèèèèè
èèèèèèèèèèè Not necessarily congruentèèèèèèèèèèèèèèèèèè
Ç B
8è Can you establish ê congruence ç ΦACE å ΦHCB if ╬A ╧ ╬Hèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèèèèèèèå ▒╖ ╧ ╜╖?
èè
èèèèèèèèèèèèèèèèèèèèèèèèèè A) Yesèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèèè B) No
@fig3308.BMP,35,40,147,74
üèèèèèShow ΦACE ╧ ΦHCB
èèèè Proç: Statementèèèèèèèèè Reason
èèèèèèèè1. ╬A ╧ ╬H, ▒╖ ╧ ╜╖èèèè 1. Given
èèèèèèèè2. m╬C = m╬Cèèèèèèèè2. Reflexive axiom
èèèèèèèè3. ╬C ╧ ╬Cèèèèèèèèè3. Defïition ç congruenceèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèè4. ΦACE ╧ ΦHCBèèèèèèè4. Congruent by ASA
Ç A
9è Can you establish ê congruence ç ΦACE å ΦHCB if ╬A ╧ ╬Hèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèèèèèå ╬CBH ╧ ╬CEA?
èè
èèèèèèèèèèèèèèèèèèèèèèèèèè A) Yesèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèèè B) No
@fig3308.BMP,35,40,147,74
üèèèèèèèè
èèè
èèèèèè
èèèèèèèèèèèèNot necessarily congruentèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
Ç B
10èèCan you establish ê congruence ç ΦACE å ΦHCB if ╬AECèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèå ╬HBC are 90° å AC = HC?
èè
èèèèèèèèèèèèèèèèèèèèèèèèèè A) Yesèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèèè B) No
@fig3308.BMP,35,40,147,74
üèèèèèShow ΦACE ╧ ΦHCB
èèèè Proç: Statementèèèèèèèè Reason
èèèèèèèè1. ╬AEC ╧ ╬HBCèèèèèè1. Given
èèèèèèèè2. AC = HCèèèèèèèè2. Given
èèèèèèèè3. ▒╖ ╧ ╜╖èèèèèèèè3. Defïition ç congruence
èèèèèèèè4. m╬C = m╬Cèèèèèèè4. Reflexive axiom
èèèèèèèè5. ╬C ╧ ╬Cèèèèèèèè5. Defïition ç congruence
èèèèèèèè6. ╬A ╧ ╬Hèèèèèèèè6. Complements ç ╬C are
èèèèèèèèèèèèèèèèèèèèèèè congruentèèèèèèèèèè
èèèèèèèè7. ΦACE ╧ ΦHCBèèèèèè7. Congruent by ASA
Ç A
11èèCan you establish ê congruence ç segments ▒└ å ╜└ ifèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèè ┤╖ ╧ ║╖ å ╬BCP ╧ ╬ECP?
èè
èèèèèèèèèèèèèèèèèèèèèèèèèè A) Yesèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèèè B) No
@fig3309.BMP,35,40,147,74
üèèèèèShow ▒┤ ╧ ╜└
èèèè Proç: Statementèèèèèèèèè Reason
èèèèèèèè1. ┤╖ ╧ ║╖, ╬BCP ╧ ╬ECPèè 1. Given
èèèèèèèè2. CP ╧ CPèèèèèèèèè2. Congruence is reflexive
èèèèèèèè3. ΦBCP ╧ ΦECPèèèèèèè3. Congruent by SAS
èèèèèèèè4. ╬CBP ╧ ╬CEPèèèèèèè4. Correspondïg parts ç
èèèèèèèèèèèèèèèèèèèèèèèè congruent Φs
èèèèèèèè5. ╬ABP ╧ ╬HEPèèèèèèè5. Supplements ç congruent
èèèèèèèèèèèèèèèèèèèèèèèè angles
èèèèèèèè6. ╬BPA ╧ ╬EPHèèèèèèè6. Vertical angles
èèèèèèèè7. ┤└ ╧ ║└èèèèèèèèè7. Correspondïg parts ç
èèèèèèèèèèèèèèèèèèèèèèèè congruent Φsèèèèèèèè
èèèèèèèè8. ΦABP ╧ ΦHEPèèèèèèè8. Congruent by ASA
èèèèèèèè9. ▒└ ╧ ╜└èèèèèèèèè9. Correspondïg parts ç
èèèèèèèèèèèèèèèèèèèèèèèè congruent Φs
Ç A
12èèCan you establish ê congruence ç angles ╬BCP å ╬ECPèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèè if ┤╖ ╧ ║╖ å ▒┤ ╧ ╜║?
èè
èèèèèèèèèèèèèèèèèèèèèèèèèè A) Yesèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèèè B) No
@fig3309.BMP,35,40,147,74
üèèè Show ╬BCP ╧ ╬ECP
èèèProç: StatementèèèèèèèèReason
èèèèèè 1. ┤╖ ╧ ╖║, ▒┤ ╧ ╜║èèè1. Given
èèèèèè 2. AB + BC = HE + ECèè 2. Addition axiom ç equality
èèèèèè 3. AC = HCèèèèèèè 3. (8)Segment addition axiom
èèèèèè 4. ▒╖ ╧ ╜╖èèèèèèè 4. Defïition ç congruenceèèèèèèèèèèèèèèèèèèèèèè
èèèèèè 5. ╬BCE ╧ ╬BCEèèèèè 5. Congruence is reflexive
èèèèèè 6. ΦACE ╧ ΦHCBèèèèè 6. Congruent by SAS
èèèèèè 7. ╬CBH ╧ ╬CEAèèèèè 7. Correspondïg partsèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèè 8. ╬ABP ╧ ╬HEPèèèèè 8. Supplements ç congruent angles
èèèèèè 9. ╬A ╧ ╬Hèèèèèèè 9. Correspondïg partsèèèèèèèèèèèèèèèèèèèèè
èèèèèè10. ΦABP ╧ ΦHEPèèèèè10. Congruent by ASA
èèèèèè11. ┤└ ╧ ║└èèèèèèè11. Correspondïg partsèèèèèèèèèèèèèèèèèèèèèè
èèèèèè12. ΦCBP ╧ ΦCEPèèèèè12. Congruent by SSS
èèèèèè13. ╬BCP ╧ ╬ECPèèèèè13. Correspondïg parts
èèèèèèèèèèèèèèèèèèèèè
Ç A
13èèèèèè Can you establish ê congruence ç ΦBCE å ΦBAEèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèè if ╬C ╧ ╬A å m╬CBE = m╬ABE = 90°?
èè
èèèèèèèèèèèèèèèèèèèèèèèèèè A) Yesèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèèè B) No
@fig3310.BMP,35,40,147,74
üèè Show ΦBCE ╧ ΦBAE
èèProç: Statementèèèèèèèè Reason
èèèèè 1. ╬C ╧ ╬Aèèèèèèèè1. Given
èèèèè 2. m╬CBE = m╬ABE = 90°èè2. Given
èèèèè 3. ╬CEB ╧ ╬AEBèèèèèè3. Complements ç congruent angles
èèèèè 4. ┤║ ╧ ┤║èèèèèèèè4. Congruence is reflexiveèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèè 5. ΦBCE ╧ ΦBAEèèèèèè5. Congruent by ASAèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
Ç A
14èèèèèè Can you establish ê congruence ç ΦBCE å ΦBAEèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèè if ┤║ ß ╖▒, ╬C ╧ ╬A, å ╖║ ╧ ▒║?
èè
èèèèèèèèèèèèèèèèèèèèèèèèèè A) Yesèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèèèèèèè B) No
@fig3310.BMP,35,40,147,74
üèèè Show ΦBCE ╧ ΦBAE
èèèProç: StatementèèèèèèèèReason
èèèèèè 1. ╬C ╧ ╬Aèèèèèèè 1. Given
èèèèèè 2. ╖║ ╧ ▒║èèèèèèè 2. Given
èèèèèè 3. ┤║ ß ╖▒èèèèèèè 3. Given
èèèèèè 4. ╬CBE å ╬ABE areèè 4. Defïition ç perpendicular
èèèèèèèèèright anglesèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèè 5. ╬CEB ╧ ╬AEBèèèèè 5. Complements ç congruent angles
èèèèèè 6. ┤║ ╧ ┤║èèèèèèè 6. Congruence is reflexive
èèèèèè 7. ΦBCE ╧ ΦBAEèèèèè 7. Congruent by ASAèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
Ç A