答：题目最后是tan6？没写全吧？是不是tan60°？[2/(a+1)+(a+2)/(a²-1)]÷[a/(a+1)]=[2(a-1)+(a+2)]/[(a+1)(a-1)]×(a+1)/a=3a/[(a+1)(a-1)]×(a+1)/a=3/(a-1)a=(-1)^2012+tan60°=1+√3所以3/(a-1)=3/(1+√3-1)=3/√3=√3
