N 2 18 July 8, 2019 16 32 64 128 N 2 180 N 2 180 formula N 2 18n 81 N 2 =- 18 9n N 2 180 proof N 2 180 degrees N 2 1800 N 2 18n 40 N 2 180 calculator N 2 18n 56 N 2 18n 40 complete the square N 2 18n 80 N 2 180 explanation N 2 18n 17 N 2 times 180