V = n h 12 ( a 1 2 + a 1 a 2 + a 2 2 ) cot ⁡ π n , {\displaystyle V={\frac {nh}{12}}\left(a_{1}^{2}+a_{1}a_{2}+a_{2}^{2}\right)\cot {\frac {\pi }{n}},} where a1 and a2 are the base and top side lengths. Pyramidal frustum