lim[x→0] (cot²x - 1/x²)=lim[x→0] (1/tan²x - 1/x²)通分=lim[x→0] (x²-tan²x)/(x²tan²x)分母用等价无穷小代换=lim[x→0] (x²-tan²x)/x⁴洛必达法则=lim...