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à 2.5èMore on Justifyïg Statements
äèPlease justify ê followïg statements.
âèèèèèèèèèèAèèèèBèèèèC
èèèèèèèèèèèèè ⌐╓╓╓╓╓╓╓╓⌐╓╓╓╓╓╓╓╓⌐
èèèèèèèèèStatementèèèèèèèè Reason
èèèèèèèèèAB + BC = ACèèèèèèè(8)Segment addition axiom
èèèè (Note ê number (8) refers ë ê eighth axiom.)
éS1 In Chapter 2 we are developïg our ability ë write deductive
proçs.èIn Section 2.1 we looked at ïductive reasonïg å saw that
you are usïg ïductive reasonïg if you observe a pattern å predict
ê outcome.èIn Section 2.2 we saw some examples ç deductive proçs
from algebra.èIn Section 2.3 we noted that each ç ê algebraic proçs
ï Section 2.2 started with a statement ç ê form "if A is true, ên
B is true."èThe hypoêsis is "A is true," å ê conclusion is "B is
true."èThis can be shortened ë "if A, ên B."
è The oêr related statements are as follows:
èèèèèèè
èèèèèèèè ConditionalèèèèIf A, ên B
èèèèèèèè Converseèèèèè If B, ên A
èèèèèèèè InverseèèèèèèIf not A, ên not B
èèèèèèèè Contrapositiveèè If not B, ên not A
è We saw that if ê origïal conditional is proven ë be true, ê
converse å ê ïverse may or may not be true.èYou are required ë
write anoêr proç ë establish eiêr ê converse or ê ïverse.
è The contrapositive, on ê oêr hå, is logically equivalent ë ê
origïal conditional.èIf you prove ê origïal conditional, ên êre
is no requirement ë prove ê contrapositive.èIt is true whenever ê
origïal conditional is true.èLikewise, ê ïverse å converse are
equivalent.
è In Section 2.4 we noted that all ç ê algebraic proçs ï Section
2.2 used a two column approach composed ç statements å reasons.èIn
this section we will contïue developïg our ability ë justify state-
ments ï a given proç.
è Consider ê followïg example.èWe would like ë show that if two
èèèèèèèèèèèèèèèèèèadjacent angles are complementary,
èèèèèèèèèèèèèèèèèèên ê angle formed by ê outside
èèèèèèèèèèèèèèèèèèrays is a right angle.
èèèèèèèèèèèèèèèèèè
@fig2501.BMP,55,140,147,74
èTheorem:èIf ╬ABE å ╬EBC are complements, ên m╬ABC = 90°.
èèProç:èStatementèèèèèèèèèèèèèèReason
èèèèèè1. ╬ABE å ╬EBC are complementsèè 1. Given
èèèèèè2. m╬ABE + m╬EBC = 90°èèèèèèè 2. _________
èèèèèè3. m╬ABC = m╬ABE + m╬EBCèèèèèè 3. (12)Angle addition
èèèèèèèèèèèèèèèèèèèèèèèèèèèaxiom
Conclusion: 4. m╬ABCè= 90°èèèèèèèèèèè4. Transitive axiom ç
èèèèèèèèèèèèèèèèèèèèèèèèèèèequality
è Can you justify ê second statement that ê m╬ABE + m╬EBC = 90°?
The answer is "defïition ç complements."è(Note ï ê above proç,
number (12) refers ë ê twelfth axiom.)
1èPlease click on "Worked" å supply ê missïg "reason" ï
èèèèèèèèèèèèèèèè ê proç.èRefer ë ê figure below.
èèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèA) (8)Segment addition axiom
èèèèèèèèèèèèèèèèèèèèB) Defïition ç adjacent angles
èèèèèèèèèèèèèèèèèèèèC) Given
@fig2502.BMP,35,40,147,74èèèèèèè D) None
ü
è Theorem: If ╣┴ bisects ▒┤, ên AP = PB
èè Proç: Statementèèèèèèèèèèèè Reason
èèèèèè1. ╣┴ bisects ▒┤èèèèèèèèè1. ______________
èèèèèè2. P is ê midpoït ç ▒┤èèèè2. Defïition ç bisects
Conclusion: 3. AP = PBèèèèèèèèèèèè3. Defïition ç midpoït
Ç C
2èPlease click on "Worked" å supply ê missïg "reason" ï
èèèèèèèèèèèèèèèè ê proç.èRefer ë ê figure below.èèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèA) Defïition ç adjacent angles
èèèèèèèèèèèèèèèèèèèèB) Defïition ç straight angle
èèèèèèèèèèèèèèèèèèèèC) (14)All right angles are
èèèèèèèèèèèèèèèèèèèèèè congruent
@fig2503.BMP,35,40,147,74èèèèèèè D) None
ü
è Theorem: If ╬APB å ╬BPC are supplementary, ên ╬APC is a straight
èèèèèèangle.
èè Proç: Statementèèèèèèèèèè Reason
èèèèèè1. ╬APB å ╬BPC areèèèèè1. Given
èèèèèèèè supplementary
èèèèèè2. m╬APB + m╬BPC = 180°èèè 2. Defïition ç supplementary
èèèèèè3. m╬APC = m╬APB + m╬BPCèèè3. (12)Angle addition axiom
èèèèèè4. m╬APC = 180°èèèèèèè 4. Transitive axiom
Conclusion: 5. ╬APC is a straight angleè 5. _______________
Ç B
3èPlease click on "Worked" å supply ê missïg "reason" ï
èèèèèèèèèèèèèèèè ê proç.èRefer ë ê figure below.
èèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèè A) Addition axiom for equations
èèèèèèèèèèèèèèèèèèèè B) (12)Angle addition axiom
èèèèèèèèèèèèèèèèèèèè C) (8)Segment addition axiomèèèèèèèèèèèèèèèèèèèèèè
@fig2504.BMP,35,40,147,74èèèèèèèèD) None
ü
è Theorem: If ╬AEB å ╬BEC are right angles, ên m╬AEB + m╬BEC = 180°
èè Proç: Statementèèèèèèèèèè Reason
èèèèèè1. ╬AEB is a right angleèèè1. Given
èèèèèè2. ╬BEC is a right angleèèè2. Given
èèèèèè3. m╬AEB = 90°èèèèèèèè3. Defïition ç right angle
èèèèèè4. m╬BEC = 90°èèèèèèèè4. Defïition ç right angle
èèèèèè5. m╬AEB + m╬BEC = 90° + 90°è5. _______________
Conclusion:èèèèèèèèè=180°
Ç A
4èPlease click on "Worked" å supply ê missïg "reason" ï
èèèèèèèèèèèèèèèè ê proç.èRefer ë ê figure below.èèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèè A) Defïition ç perpendicular
èèèèèèèèèèèèèèèèèèèèèèèbisecër
èèèèèèèèèèèèèèèèèèèè B) Defïition ç perpendicular
èèèèèèèèèèèèèèèèèèèèèèèlïes
@fig2505.BMP,35,40,147,74èèèèèèèèC) (13)Angle bisecër is uniqueèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
ü
è Theorem: If m╬BPC = 90°, ên ░╕ ß │┴
èè Proç: StatementèèèèèèèèèèèReason
èèèèèè1. m╬BPC = 90°èèèèèèèè 1. Given
èèèèèè2. ╬BPC is a right angleèèè 2. Defïition ç right angle
èèèèèè3. ░╕ å │┴ ïtersect atèèè3. Defïition ç ïtersect at
èèèèèèèè right anglesèèèèèèèèè right angle
Conclusion: 4. ░╕ å │┴ areèèèèèèè 4. ________________
èèèèèèèè perpendicular lïesèèèèè
Ç B
5èPlease click on "Worked" å supply ê missïg "reason" ï
èèèèèèèèèèèèèèèè ê proç.èRefer ë ê figure below.èèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèè A) (8)Segment addition axiomèèèèèèèèèèèèèèèèèèèèèè
èèèèèèAè Bè Cè EèèèèèèèèèB) Defïition ç collïearèèèèèèèèèèèèèèèèèèèèè
èèèè ₧╓╓£╓╓╓£╓╓╓£╓╓╓£╓╓¥èèèèèèè C) (16)Distance between two
èèèèèèèèèèèèèèèèèèèèèèèèpoïts is uniqueèè
èèèèèèèèèèèèèèèèèèèèè D) Defïition ç congruentèèèèèèèèèèèèèèèèèèèèèèèèèèè
ü
è Theorem: If AB = BC å BC = CE, ên ▒┤ ╧ ╖║
èè Proç: Statementèèèèèèèèè Reason
èèèèèè1. AB = BCèèèèèèèèè1. Given
èèèèèè2. BC = CEèèèèèèèèè2. Given
èèèèèè3. AB = CEèèèèèèèèè3. Transitive axiom ç equalityèèèèèèèè
Conclusion: 4. ▒│ ╧ ╖╣èèèèèèèèè4. _________________èèèèè
Ç D
6èPlease click on "Worked" å supply ê missïg "reason" ï
èèèèèèèèèèèèèèèè ê proç.èRefer ë ê figure below.
èèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèA) Defïition ç adjacent anglesèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèB) (13)Angle bisecër is uniqueèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèèC) (12)Angle addition axiomèèè
@fig2506.BMP,35,40,147,74èèèèèèè D) Noneèèèèèèèèèèèèèèèèèèèèèèèèèèè
ü
è Theorem: If m╬BAD = 45° å m╬CAD = 25°,
èèèèèèên m╬BAC = 20°.
èè Proç: StatementèèèèèèèèèReason
èèèèèè1.m╬BAD = 45°, m╬CAD = 25° 1. Given
èèèèèè2. m╬BAD = m╬BAC + m╬CADè 2. __________________
èèèèèè3. m╬BAD - m╬CAD = m╬BACè 3. Subtraction axiom ç equationsèèèèèèèè
èèèèèè4.è45° - 25° = m⌠BACèèè4. Substitution axiom
Conclusion: 5.èè 20° =èm╬BACèèèè5. Distributive axiom
Ç C
7èPlease click on "Worked" å supply ê missïg "reason" ï
èèèèèèèèèèèèèèèè ê proç.èRefer ë ê figure below.èèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèè A) Defïition ç angle bisecërèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèè B) (14)All right angles are
èèèèèèèèèèèèèèèèèèèèèèècongruentèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèèè C) (13)Angle bisecër is uniqueèèè
@fig2506.BMP,35,40,147,74èèèèèèèèD) Noneèèèèèèèèèèèèèèèèèèèèèèèèèèè
ü
è Theorem: If ▒╕ bisects ╬DAB, ên ╬BAC ╧ ╬CAD
èè Proç: StatementèèèèèèèèèèReason
èèèèèè1. ▒╕ bisects ╬DABèèèèè 1. Given
èèèèèè2. m╬BAC = m╬CADèèèèèè 2. _________________
Conclusion: 3. ╬BAC ╧ ╬CADèèèèèèè 3. Defïition ç congruentèèèèèèèèèèèèèèèèèèèèèèèè
Ç A
8èPlease click on "Worked" å supply ê missïg "reason" ï
èèèèèèèèèèèèèèèè ê proç.èRefer ë ê figure below.èèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèè A) Lïes 2 & 3, Transitive axiom
èèèèèèèèèèèèèèèèèèèèèèç equality
èèèèèèèèèèèèèèèèèèè B) (10)Measure ç angle is uniqueèèèèèèèèèèèèèèèèèèèèèè
èèèèèèèèèèèèèèèèèèè C) (12)Angle addition axiomèèè
@fig2507.BMP,35,40,147,74èèèèèèèD) Noneèèèèèèèèèèèèèèèèèèèèèèèèèèè
ü
è Theorem: If ╬PSQ å ╬QSR are complementary, ên ╬PSR is a
èèèèèèright angle
èè Proç: Statementèèèèèèèèèè Reason
èèèèèè1. ╬PSQ å ╬QSR areèèèèè1. Given
èèèèèèèè complementary
èèèèèè2. m╬PSQ + m╬QSR = 90°èèèè2. Defïition ç complementary
èèèèèè3. m╬PSR = m╬PSQ + m╬QSRèèè3. (12)Angle addition axiomèè
èèèèèè4. m╬PSR = 90°èèèèèèèè4. __________________
Conclusion: 5. ╬PSR is a right angleèèè5. Defïition ç right angleèèèèèèèèèèèèèèèèèèèèèèèè
Ç A
è