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Ex 8.1, 2 - If diagonals of a parallelogram are equal - Opposite sides of parallelogram

Ex 8.1, 2 - Chapter 8 Class 9 Quadrilaterals - Part 2

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Ex 8.1, 2 If the diagonals of a parallelogram are equal, then show that it is a rectangle. Given: Let ABCD be a parallelogram where AC = BD To prove: ABCD is a rectangle Proof: Rectangle is a parallelogram with one angle 90 We prove that one of its interior angles is 90 . In ABC and DCB, AB = DC BC = BC AC = DB ABC DCB ABC = DCB Now, AB DC & BC is a transversal B + C= 180 B + B = 180 2 B = 180 B = "180 " /"2" = 90 So, ABCD is a parallelogram with one angle 90 ABCD is a rectangle

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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.