Posted by **polygon** on Wednesday, March 28, 2012 at 1:43am.

each interior angle of a regular polygon is 18 degree more than eight times an exterior angle. the number os sides of polygon is.

- maths -
**Steve**, Wednesday, March 28, 2012 at 11:14am
at each vertex, interior + exterior = 180 degrees.

If exterior = x,

x+(8x+18) = 180

9x = 162

x = 18

he exterior angle of a regular n-gon is 360/n, so

18 = 360/n

n = 20

- maths -
**drwls**, Wednesday, March 28, 2012 at 11:22am
Interior angle = 180 - (exterior angle) = 180 -360/N

Exterior angle = 360/N

180 - (360/N) = [8*360/N] +18

9*360/N = 162

N = 20 sides

It is called an icosagon

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