Lim((tanx-sinx)/x^3)怎麼做x->0

Lim((tanx-sinx)/x^3)怎麼做x->0

Lim(x-->0)((tanx-sinx)/x^3)
=lim(x-->0)(sec²;x-cosx)/(3x²;)(羅比達法則)
=lim(x-->0)(2secx*secxtanx+sinx)/(6x)(羅比達法則)
=lim(x-->0)(2sec³;x*sinx+sinx)/(6x)
=lim(x-->0)(2sec³;x+1)/6*(sinx/x)
=1/2