tg[arctan(w/2)+arctan(w/3)]=tg(π/6)[tg[arctan(w/2)]+tg[arctan(w/3)]]/[1-tg[arctan(w/2)]tg[arctan(w/3)]]=1/√3(w/2+w/3)/(1-w^2/6)=1/√3w^2+5√3w-6=0解得w=(-5√3±3√11)/2