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.

(iii) Heptagon

There are 7 sides in a heptagon

The sum of the interior angles of the heptagon is:

(7 – 2) π = 5π

Therefore, each angle of heptagon is equal to:

= 5π/7 × 180^o/ π

= 900^o/7

= 128^o 34′ 17”

(iv) Duodecagon

There are 12 sides in a duodecagon

The sum of the interior angles of the duodecagon is:

(12 – 2) π = 10π

Therefore, each angle of duodecagon is:

= 10π/12 × 180^o/ π

= 150^o