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Theorem 6.5 - Class 9 - If interior angles are supplementary, lines.jpg

Theorem 6.5 - Chapter 6 Class 9 Lines and Angles - Part 2

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Theorem 6.5 :- If a transversal intersects two lines, such that the pair of interior angles on the same side of the transversal is supplementary, then the two lines are parallel. Given :- Two parallel lines AB and CD and a transversal PS intersecting AB at Q and CD at R such that BQR + DRQ = 180 To Prove :- AB CD. Proof :- For lines PS DRQ + DRS = 180 But, BQR + DRQ = 180 From (1) & (2) DRQ + DRS = BQR + DRQ DRS = BQR But they are corresponding angles. Thus, for lines AB & CD with transversal PS, corresponding angles are equal Hence AB and CD are parallel. Hence proved

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.