Question 1012114
{(n-2)/n}*180 is interior angle
exterior angle is 1/8 of that or {(n-2)/n}*22.5
The two add to 180
[180n-360]/n +[22.5n-45]/n=180
multiply by n
180n-360+22.5n-45=180n
22.5 n=405
n=18
18 sides