求x趋于0的lim{1+1/2x^2-（1+x^2)^1/2}/{(cosx-e^(x^2))sin(x^2)

Taylor展式：原极限＝lim{1+1/2x^2-(1+1/2x^2+(1/2)(-1/2)/2x^4+小o(x^4))}/{[1-x^2/2-(1+x^2)+小o(x^2)]x^2}=lim[1/8x^4+小o(x^4)]/[－3/2x^4+小o(x^4)]=－1/12.