An interior angle of a regular polygon = (2n−4)×90n An exterior angle of a regular polygon = 360n (2n−4)×90n =5 × 360n (Given) = (2n-4) x 90 = 5 x 360 = 180n - 360 = 1800 = 180n = 1800 + 360 = 180n = 2160 = n = 2160180 = 12 The polygon has 12 sides which is dodecagon
