求极限x→0lim[x²sin(1/x)]
x→0时,x是无穷小量；1/x是无穷大量,但︱sin(1/x)︱≦1,即-1≦sin(1/x)≦1,是有界变
量(上下有界)；∴x→0lim[x²sin(1/x)]=0.