求极限:lim(x→0+)ln(sinax)/ln(sinbx) (a>0,b>0)

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求极限:lim(x→0+)ln(sinax)/ln(sinbx) (a>0,b>0)
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求极限:lim(x→0+)ln(sinax)/ln(sinbx) (a>0,b>0)
求极限:lim(x→0+)ln(sinax)/ln(sinbx) (a>0,b>0)

求极限:lim(x→0+)ln(sinax)/ln(sinbx) (a>0,b>0)
不定式,最好用洛必达法则上下分别求导了
lim(x→0+) ln(sinax)/ln(sinbx)
=lim(x→0+) (1/sinax*acosax)/(1/sinbx*bcosbx),用洛必达法则
=(a/b)lim(x→0+) tanbx/tanax
=(a/b)lim(x→0+) [bsec^2(bx)]/[asec^2(ax)],用洛必达法则
=(a/b)(b/a)lim(x→0+) cos^2(ax)/cos^2(bx)
=1*1/1
=1

这事0/0型,运用洛比达法则