Question

anybody please give me answer

Answer 1

For any regular  polygon, the magnitude of an interior angle is (n-2)*180 deg/n, where n is the number of sides. For a regular Pentagon,
internal angle is (5-2)*180 deg/5.
            which is 108 deg.

For conversion of degrees into radians multiply by 'pi' and divide by 180 deg.

So, 108° = 3π/5.



Similarly for Hexagon and Octagon substitute 'n' as 6 and 8 in
 (n-2)*180 deg/n. 



Hope this helps you out.