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2 Theorem 7.8 - Class 9 - Similarly we can Prove AB + BC  AC.jpg

Theorem 7.8 - Class 9 - Sum of two sides of triangle is greater than.jpg

  1. Chapter 7 Class 9 Triangles
  2. Serial order wise
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Transcript

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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CA Maninder Singh is a Chartered Accountant for the past 8 years. He provides courses for Practical Accounts, Taxation and Efiling at teachoo.com .
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