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Section 4.3 & 4.4: Proving s are Congruent. Goals. Identify figures and corresponding parts Prove that 2 are . Anchors. Identify and/or use properties of congruent and similar polygons Identify and/or use properties of triangles. M. Q. N. R. P. S.
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Section 4.3 & 4.4: Proving s are Congruent Goals • Identify figures and corresponding parts • Prove that 2 are Anchors • Identify and/or use properties of congruent and similar polygons • Identify and/or use properties of triangles
M Q N R P S Side-Side-Side (SSS) Postulate • If 3 sides of 1 are to 3 sides of a 2nd , then the 2 ’s are . If Side MN QR Side NP RS and Side PM SQ Then MNP QRS Then we can say: M Q, N R , and P S
Statements Reasons Given: W is the midpoint of QS PQ TS and PW TWProve: PQW TSW • W is the mdpt of QS, • PQ TS and PW TW • Given 2) QW SW 2) Def. of midpoint 3) PQW TSW 3) SSS
Statements Reasons Given: D is the midpoint of ACABC is isosceles ABC is the vertex angleProve: ABD CBD • D is the mdpt of AC, • ABC is isosceles • Given 2) AD DC 2) Def. of midpoint 3) AB BC 3) Property of Isosceles 4) BD BD 4) Reflexive 5) ABD CBD 5) SSS
Q X ) P W S Y ) Side-Angle-Side (SAS) Postulate • If 2 sides and the included of 1 are to 2 sides and the included of a 2nd , then the 2 s are . If Side PQ WX Angle Q X Side QS XY Then PQS WXY Then we can say: PS WY, P W , and S Y
Statements Reasons Given: QRS is isosceles RT bisects QRS QRS is the vertex angle Prove: QRT SRT ) • QRS is isosceles • RT bisects QRS • Given 2) QRT SRT 2) bisector 3) QR RS 3) Property of Isosceles 4) RT RT 4) Reflexive 5) QRT SRT 5) SAS
Statements Reasons Given: BD and AE bisect each otherProve: ABC EDC ) ) • BD and AE bisect • each other • Given 2) BC CD, AC CE 2) Segment bisectors 3) BCA ECD 3) Vertical angles 4) ABC EDC 4) SAS
) Q M ) R N S P ) ) Angle-Side-Angle (ASA) Postulate • If 2 ’s and the included side of 1 are to 2 ’s and the included side of a 2nd, then the 2 are If Angle N R Side MN QR Angle M Q Then MNP QRS Then we can say: MP QS, NP RS , and P S
) ) Statements Reasons Given: B N RW bisects BNProve: BRO NWO ) ) • B N • RW bisects BN • Given 2) BOR WON 2) Vertical Angles 3) BO ON 3) Segment bisector 4) BRO NWO 4) ASA
) 1 3 4 2 Statements Reasons Given: 1 2 CD bisects BCEProve: BCD ECD ) ) • 1 2 • CD bisects BCE • Given 2) 3 4 • Supplements of congruent s are congruent 3) BCD ECD 3) Angle bisector 4) BCE is isosceles 4) Property of isosceles 5) BC CE 5) Property of isosceles 6) BCD ECD 6) ASA
X Q ( ( W P Y S ( ( Angle-Angle-Side (AAS) Theorem • If 2 ’s and a non-included sideof 1 are to 2 ‘s and a non-included side of a 2nd , then the 2 ’s are . If Angle P W Angle S Y Side QP WX Then PQS WXY Then we can say: QS XY, PS WY , and Q X
) ) Statements Reasons Given: AD ║ EC , B is the mdpt of CDProve: ABD EBC ) ) 1) AD ║ EC , B is the mdpt of CD • Given 2) A E 2) Alternate Interior s 3) ABD CBE 3) Vertical Angles 4) BD BC 4) Midpoint 5) ABD EBC 5) AAS
) ) Statements Reasons Given: AD ║ EC , B is the mdpt of CDProve: ABD EBC ) ) 1) AD ║ EC , B is the mdpt of CD • Given 2) A E, D C 2) Alternate Interior s 3) BD BC 3) Midpoint 4) ABD EBC 4) AAS
40 40 50 50 Why Angle-Angle-Angle (AAA)Doesn’t Work The angles are , but the sides are proportional.
E ( A D F ( C B Why Side-Side-Angle (SSA)Doesn’t Work Two different triangles can be formed if you use two sides and a non-included angle.
Theorem 4.8: Hypotenuse-Leg (HL) Theorem • If the hypotenuse and a leg of a right are to a hypotenuse and a leg of a 2nd right , then the 2 ’s are D A If BC EF and AC DF, then ABC DEF Special case of SSA B C E F Then we can say: AB DE, A D , and C F
Statements Reasons Given: RS QT QRT is isosceles QRT is the vertex angleProve: QRS TRS 1) RS QT, QRT is isosceles • Given 2) QSR 90, TSR 90 2) Definition of perpendicular 3) QSR TSR 3) Substitution 4) QR RT 4) Property of isosceles 5) RS RS 5) Reflexive 6) QRS TRS 6) HL