fact: Definition pue_formula (p : pt) (a : pt) (b : pt) : Q := let: Bpt p_x p_y := p in let: Bpt a_x a_y := a in let: Bpt b_x b_y := b in ((b_x * p_y - p_x * b_y - (a_x * p_y - p_x * a_y) + a_x * b_y - b_x * a_y))%Q.
imports: mathcomp(all_ssreflect) ZArith QArith List String OrderedType OrderedTypeEx FMapAVL