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 Find the magnitude, in radians and degrees, of the interior angle of a regular: (i) Pentagon (ii) Octagon

Solution:

This is known that the sum of the interior angles of a polygon is equal to (n – 2) π, where n represents the number of sides in the given polygon.

Each angle of a polygon is equal to the sum of the interior angles of the polygon/number of sides.

(i) Pentagon

We know that there are 5 sides to the pentagon. Therefore n = 5

Using the above relation, the sum of interior angles of the pentagon is given by:

(5 – 2) π = 3π

Therefore, each angle of pentagon is:

= 3π/5 × 180o/ π

= 108o

(ii) Octagon

Similarly, there are 8 sides to an octagon

Therefore, the sum of interior angles of the octagon is given by:

= (8 – 2) π

= 6π

Thus, each angle of the octagon is:

= 6π/8 × 180o/ π

= 135o