tan(πx/2）吧?lim(x→1) (1-x)tan(πx/2)＝lim(x→1) (1-x) sin(πx/2)/cos(πx/2)＝lim(x→1) (1-x) /cos(πx/2)＝lim(x→1) (1-x) /sin(π/2-πx/2)＝lim(x→1) (1-x) /(π/2-πx/2)＝2/π希望采纳...