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Theorem 6.7 - Class 9 - Sum of all angles are triangle is 180.jpg

Theorem 6.7 - Chapter 6 Class 9 Lines and Angles - Part 2


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Theorem 6.7 :- The sum of all angles are triangle is 180°. Given :- Δ PQR with angles ∠1, ∠2 and ∠3 Prove :- ∠1 + ∠2 + ∠3 = 180° Construction:- Draw a line XY passing through P parallel to QR Proof: Also, for line XY ∠1 + ∠4 + ∠5 = 180° ∠1 + ∠2 + ∠3 = 180° Hence, sum of all angle of a triangles are equal. 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 12 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.