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Addition & Subtraction Properties. Lesson 2.5. 3 cm. 7 cm. 7 cm. A. B. C. D. In the diagram above, AB = CD. Do you think that AC = BD? Suppose that BC were 3cm. Would AC = BD? If AB = CD, does the length of BC have any effect on whether AC = BD?. Yes. Yes. No. Theorem 8:.
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Addition & Subtraction Properties Lesson 2.5
3 cm 7 cm 7 cm A B C D • In the diagram above, AB = CD. • Do you think that AC = BD? • Suppose that BC were 3cm. Would AC = BD? • If AB = CD, does the length of BC have any effect on whether AC = BD? Yes Yes No
Theorem 8: • If a segment is added to two congruent segments, the sums are congruent (Addition Property) P Q R S Given: PQ RS Conclusion: PR QS Proof:PQ RS, so by definition of congruent segments, PQ = RS. Now, the Addition Property of Equality says that we may add QR to both sides, so PQ + QR = RS + QR. Substituting, we get PQ = QS. Therefore, PR QS by the definition of congruent segments.
Theorem 9: • If an angle is added to two congruent angles, the sums are congruent. (Addition Property) Is EFH necessarily congruent to JFG?
Theorem 10: • If congruent segments are added to congruent segments, the sums are congruent. (Addition Property) Do you think that KM is necessarily congruent to PO?
Theorem 11: • If congruent angles are added to congruent angles, the sums are congruent. (Addition Property) Is TWX necessarily congruent to TXW?
Theorem 12: • If a segment (or angle) is subtracted from congruent segments (or angles), the differences are congruent. (Subtraction Property) If KO = KP and NO = RP, is KN = KR?
Theorem 13: • If congruent segments (or angles) are subtracted from congruent segments (or angles) the differences are congruent. (Subtraction Property) • The only difference between Theorem 12 and 13 is that this one is plural.
Given Given If angles are subtracted from angles, the differences are . (Subtraction property) 1. NOP NPO 2. ROP RPO 3. NOR NPR
HEF is supp. to EHG. GFE is supp. to FGH. EHF FGE GHF HGE EHG FGH HEF GFE Given Given Given Given If angles are added to angles, the sums are . (Addition Property) Supplements of s are .