lim(x→π)[(sin3x)/(x-π)],用洛必达法则=lim(x→π)[3cos3x]=3cos(3π)=3*(-1)=-3lim(x→π/2)[(1+cosx)^(secx)]=lim(x→π/2)[(1+cosx)^(1/cosx)],用y=1/cosx=lim(y→∞)[(1+1/y)^y]=e