Let us consider a triangle ∆ ABC

 

Let ∠ 1 be the exterior angle

13.jpg

 

Since BAD is a line

  ∠ A + ∠1 = 180°      (Linear Pair)

  ∠ 1 = 180° − ∠ A

 

So, in a polygon

  Interior angle + Exterior angle = 180°

  1. Chapter 3 Class 8 Understanding Quadrilaterals
  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.