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Ex 6.5, 5 - Chapter 6 Class 10 Triangles - Part 2

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Ex 6.5, 5 ABC is an isosceles triangle with AC = BC. If AB2 = 2AC2, prove that ABC is a right triangle. Given: ABC is an isosceles triangle. where, AC = BC & AB2 = 2 AC2 To prove: ABC is a right angle triangle . Proof: Given AB2 = 2AC2 AB2 = AC2 + AC2 AB2 = AC2 + BC2 So, AB will be the largest side, i.e. Hypotenuse = AB Now, we prove Pythagoras theorem , (Hypotenuse)2 = (Height )2 + (Base)2 L.H.S (Hypotenuse)2 = AB2 R.H.S (Height )2 + (Base)2 = (AC)2 + (BC)2 = (AC)2 + (AC)2 (Given AC = BC) = 2(AC)2 = AB2 (Given AB2 = 2AC2) Since L.H.S = R.H.S , Pythagoras theorem is satisfied Hence ABC is a right angled triangle

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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.