当x趋向于0+时,limln(sin3x)/ln(sinx)的极限

问题描述:

当x趋向于0+时,limln(sin3x)/ln(sinx)的极限

lim(x→0+) ln(sin3x)/ln(sinx)
=lim(x→0+) [3cos3x/(sin3x)/[cosx/sinx]
=lim(x→0+) (3sinx/sin3x=1[3cos3x/(sin3x)/[cosx/sinx]怎么会得出(3sinx)/(sin3x)????不明白cosxcos3x趋于1,不管它