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Learn in your speed, with individual attention - Teachoo Maths 1-on-1 Class


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Theorem 7.8 :- The sum of any two sides of a triangle is greater than the third side. Given :- A triangle ABC To Prove :- AB + AC > BC . Construction:- Extend AB to D such that AD = AC Proof:- In Δ ACD AD = AC ∴ ∠1 = ∠2 Now, ∠BCD = ∠BCA + ∠1 = ∠BCA + ∠2 > ∠2 Now, in ∆BCD ∠BCD > ∠2 ⇒ BD > BC ⇒ AB + AD > BC ⇒ AB + AC > BC Similarly we can prove AB + BC > AC & AC + BC > AB 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 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.