原式=lim[（1-sin^2(x）)^(1/sin^2(x）)]^(0.5*sinx)=e^0=1
L = lim(x→0)(cosx))^(1/sinx)lnL = lim(x→0)ln(cosx))/sinx (0/0) = lim(x→0)[-sinx/cosx]/cosx =0L =e^0 = 1lim(x→0)(cosx))^(1/sinx) =1
