tan5分之π+tan5分之2π+tan5分之3π+tan5分之4π怎么算
问题描述：
tan5分之π+tan5分之2π+tan5分之3π+tan5分之4π怎么算
答
原式=tan(π-4π/5）+tan(π-3π/5)+tan(3π/5)+tan(4π/5)=-tan4π/5+(-tan3π/5))+tan(3π/5)+tan(4π/5)=0
答
tanA+tanB=sin(A+B)/cosAcosB=tan(A+B)(1-tanAtanB) tanπ/5+tan2π/5+tan3π/5+tan4π/5=tanπ/5+tan4π/5+tan2π/5+tan3π/5=tan(π/5+4π/5)(1-tanπ/5*tan4π/5)+tan(π2/5+3π/5)(1-tan2π/5*tan3π/5)=tanπ*(...