设排除的角为α,内角和为760 + α度
设为n边形,其内角和为180(n - 2) = 760 + α
n - 2 = (760 + α)/180
n = 2 + (720 + 40 + α)/180
= 2 +720/180 + (40 + α)/180
= 2 + 4 + (40 + α)/180
= 6 + (40 + α)/180
(40 + α)/180须为整数
因为0 < α < 180,40 < 40 + α < 220,40和220之间180的倍数只有180,此时(40 + α)/180 = 1
n = 6 + 1 = 7