多邊形的題目

If the sum of the interior angles of a polygon is 4 times the sum of its exterior angles ,find the number of sides of this polygon.
Let x be the no. of sides of polygon
Then the sum of the interior angles= (x-2)*180 degree
and the sum of the exterior angle=360 degree
(x-2)*180=360*4
x-2=8
x=10
The no. of sides of polygon is 10

exterior angles=360 degrees
interior angles = 360x4 = 1440 degrees
let n be the no. of the sides of the polygon
(n-2)180 = 1440
n-2 = 8
n=10

the polygon has 10 sides