Isosceles triangle is a triangle where

  • Two sides are equal
  • Angles opposite to equal sides are equal

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Here,

  • a is the side which is equal, AB = AC
  • b is the base, BC = b
  • Angles opposite to equal sides are equal, ∠B = ∠C (Proof - link)

 

Perimeter

Perimeter of isosceles triangle = Sum of all sides

= a + a + b

= 2a + b

 

Perimeter of isosceles triangle = 2a + b

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Properties of Isosceles triangle

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  • Two sides are equal
  • Angles opposite to equal sides are equal
  • Altitude is the median

∴ AD ⊥ BC

& D is the mid – point of BC

 

 

  1. Chapter 6 Class 7 Triangle and its Properties
  2. Concept wise
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Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 8 years. He provides courses for Maths and Science at Teachoo. You can check his NCERT Solutions from Class 6 to 12.