当x趋于0+时,lim (ln tan7x)/(ln tan2x)怎么求,

当x趋于0+时,lim (ln tan7x)/(ln tan2x)怎么求,
当x趋于0+时,lim (ln tan7x)/(ln tan2x)怎么求,

当x趋于0+时,lim (ln tan7x)/(ln tan2x)怎么求,
=lim (ln sin7x - ln cos7x)/(ln sin2x - ln cos2x)
=lim (ln sin7x - 0)/(ln sin2x - 0)
=lim (ln sin7x )/(ln sin2x )
利用洛笔答法则得
=lim (7·cos7x/ sin7x )/(2·cos2x/ sin2x )
=lim (7·cos7x·sin2x)/( 2·sin7x·cos2x )
=lim (7×1×2x)/( 2×1×7x )
=1