UPSC NDA I 2021 Mathematics Solved Paper

Concept:
The interior angle of a regular polygon is given by:
(n−2)×‌

180∘

n

Where, n= number of sides
Interior Angle =180∘ - Exterior Angle
Calculation:
Regular Octagon has 8 sides
so, n=8
Interior Angle
‌‌=(n−2)×‌

180∘

n

‌‌=(8−2)×‌

180∘

8

‌‌=6×‌

180∘

8

‌‌=‌

3π

4