x→1lim (1-x)tan(πx/2)=lim tan(πx/2) / 1/(1-x)此时,极限为∞/∞型,利用L'Hospital法则=lim (tan(πx/2))' / (1/(1-x))'=lim (π/2)/(cos(πx/2))^2 / 1/(1-x)^2=(π/2)*lim (1-x)^2 / (cos(πx/2))^2此时,极限...