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2.5 Proving Statements about Line Segments. Theorems are statements that can be proved. Theorem 2.1 Properties of Segment Congruence Reflexive AB ≌ AB All shapes are ≌ to them self Symmetric If AB ≌ CD, then CD ≌ AB Transitive If AB ≌ CD and CD ≌ EF, then AB ≌ EF.
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Theorems are statements that can be proved Theorem 2.1 Properties of Segment Congruence Reflexive AB ≌ AB All shapes are ≌ to them self Symmetric If AB ≌ CD, then CD ≌ AB Transitive If AB ≌ CD and CD ≌ EF, then AB ≌ EF
How to write a Proof Proofs are formal statements with a conclusion based on given information. One type of proof is a two column proof. One column with statements numbered; the other column reasons that are numbered.
Given: EF = GH Prove EG ≌ FH E F G H #1. EF = GH #1. Given
Given: EF = GH Prove EG ≌ FH E F G H #1. EF = GH #1. Given #2. FG = FG #2. Reflexive Prop.
Given: EF = GH Prove EG ≌ FH E F G H #1. EF = GH #1. Given #2. FG = FG #2. Reflexive Prop. #3. EF + FG = GH + FG #3. Add. Prop.
Given: EF = GH Prove EG ≌ FH E F G H #1. EF = GH #1. Given #2. FG = FG #2. Reflexive Prop. #3. EF + FG = GH + FG #3. Add. Prop. #4. EG = EF + FG #4. FH = FG + GH
Given: EF = GH Prove EG ≌ FH E F G H #1. EF = GH #1. Given #2. FG = FG #2. Reflexive Prop. #3. EF + FG = GH + FG #3. Add. Prop. #4. EG = EF + FG #4. Segment Add. FH = FG + GH
Given: EF = GH Prove EG ≌ FH E F G H #1. EF = GH #1. Given #2. FG = FG #2. Reflexive Prop. #3. EF + FG = GH + FG #3. Add. Prop. #4. EG = EF + FG #4. Segment Add. FH = FG + GH #5. EG = FH #5. Subst. Prop.
Given: EF = GH Prove EG ≌ FH E F G H #1. EF = GH #1. Given #2. FG = FG #2. Reflexive Prop. #3. EF + FG = GH + FG #3. Add. Prop. #4. EG = EF + FG #4. Segment Add. FH = FG + GH #5. EG = FH #5. Subst. Prop. #6. EG ≌ FH #6. Def. of ≌
Given: RT ≌ WY; ST = WXR S TProve: RS ≌ XYW X Y #1. RT ≌ WY #1. Given
Given: RT ≌ WY; ST = WX R S TProve: RS ≌ XY W X Y #1. RT ≌ WY #1. Given #2. RT = WY #2. Def. of ≌
Given: RT ≌ WY; ST = WX R S TProve: RS ≌ XY W X Y #1. RT ≌ WY #1. Given #2. RT = WY #2. Def. of ≌ #3. RT = RS + ST #3. Segment Add. WY = WX + XY
Given: RT ≌ WY; ST = WX R S TProve: RS ≌ XY W X Y #1. RT ≌ WY #1. Given #2. RT = WY #2. Def. of ≌ #3. RT = RS + ST #3. Segment Add. WY = WX + XY #4. RS + ST = WX + XY #4. Subst. Prop.
Given: RT ≌ WY; ST = WX R S TProve: RS ≌ XY W X Y #1. RT ≌ WY #1. Given #2. RT = WY #2. Def. of ≌ #3. RT = RS + ST #3. Segment Add. WY = WX + XY #4. RS + ST = WX + XY #4. Subst. Prop. #5. ST = WX #5. Given
Given: RT ≌ WY; ST = WX R S TProve: RS ≌ XY W X Y #1. RT ≌ WY #1. Given #2. RT = WY #2. Def. of ≌ #3. RT = RS + ST #3. Segment Add. WY = WX + XY #4. RS + ST = WX + XY #4. Subst. Prop. #5. ST = WX #5. Given #6. RS = XY #6. Subtract. Prop.
Given: RT ≌ WY; ST = WX R S TProve: RS ≌ XY W X Y #1. RT ≌ WY #1. Given #2. RT = WY #2. Def. of ≌ #3. RT = RS + ST #3. Segment Add. WY = WX + XY #4. RS + ST = WX + XY #4. Subst. Prop. #5. ST = WX #5. Given #6. RS = XY #6. Subtract. Prop. #7. RS ≌ XY #7. Def. of ≌
Given: x is the midpoint of MN and MX = RXProve: XN = RX #1. x is the midpoint of MN #1. Given
Given: x is the midpoint of MN and MX = RXProve: XN = RX #1. x is the midpoint of MN #1. Given #2. XN = MX #2. Def. of midpoint
Given: x is the midpoint of MN and MX = RXProve: XN = RX #1. x is the midpoint of MN #1. Given #2. XN = MX #2. Def. of midpoint #3. MX = RX #3. Given
Given: x is the midpoint of MN and MX = RXProve: XN = RX #1. x is the midpoint of MN #1. Given #2. XN = MX #2. Def. of midpoint #3. MX = RX #3. Given #4. XN = RX #4. Transitive Prop.
Something with Numbers If AB = BC and BC = CD, then find BC A D 3X – 1 2X + 3 B C
Homework Page 105 # 6 - 11
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