Simonearctan1+arctan2+arctan3=
的有关信息介绍如下：
设arctan1+arctan2+arctan3=x 那么tanx=tan(arctan1+arctan2+arctan3) =(tan(arctan1+arctan2)+tan(arctan3))/(1-tan(arctan1+arctan2)tan(arctan3) =(tan(arctan1+arctan2)+3)/(1-tan(arctan1+arctan2)*3) 又tan(arctan1+arctan2)=(tan(arctan1)+tan(arctan2))/(1-tan(arctan1)*tan(arctan2))=(1+2)/(1-2) =-3 所以tanx=(-3+3)/(1-(-3)*3)=0 而arctan1 arctan2 arctan3 都是锐角 故有x=π,即arctan1+arctan2+arctan3=π
