Find the measure of each
exterior angle of a regular polygon of:
(1) 8 sides
(2) 12 sides
Answers
we know that,
sum of all the interior angles = (no. of sides - 2) × 180
so, in an regular octagon(polygon with 8 sides)
sum of all the interior angles = (no. of sides - 2) × 180
= (8 - 2) × 180
= 6 × 180
= 1080
sum of all the interior angles of an octagon = 1080
measure of a single interior angle = sum of all the interior angles/total sides
= 1080/8
= 135
we know that an interior and an exterior angle of a regular polygon is always supplementary(supplementary means the two angle sums up to 180)
let the exterior angle be x
so, 135 + x = 180
⇒ x = 180 - 135
= 45
so, in a regular do-decagon(polygon with 12 sides)
sum of all the interior angles = (no. of sides - 2) × 180
= (12-2) × 180
= 10 × 180
= 1800
sum of all the interior angles of an do-decagon = 1800
measure of a single interior angle = 1800/12
= 150
let the exterior angle be y
so, 150 + y = 180
⇒ y = 180 - 150
= 30
exterior angle of a regular polygon of 8 sides = 45
exterior angle of a regular polygon of 12 sides = 30