Theorem Class 9th Ch 7 v3.0 after video.jpg

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  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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Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He provides courses for Mathematics from Class 9 to 12. You can ask questions here.
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