Question Number 25985 by Vignesh vkj last updated on 17/Dec/17
$$\mathrm{In}\:\mathrm{a}\:\bigtriangleup{ABC},\:{a}\:\mathrm{cot}\:{A}+\:{b}\:\mathrm{cot}\:{B}+{c}\:\mathrm{cot}\:{C}\:= \\ $$
Answered by ajfour last updated on 17/Dec/17
$$\Sigma{a}\mathrm{cot}\:{A}\:=\Sigma\sqrt{\mathrm{4}{R}^{\mathrm{2}} −{a}^{\mathrm{2}} } \\ $$$${R}\:{is}\:{the}\:{circumradius}\:. \\ $$