åå¼=lim(xâ0)(tanx-x)/x^3 ï¼çä»·æ ç©·å°ï¼
=lim(xâ0)(1/cos^2(x)-1)/(3x^2) ï¼æ´å¿
è¾¾æ³åï¼
=lim(xâ0)sin^2(x)/(3x^3)*1/cos^2(x)
=1/3 ï¼çä»·æ ç©·å°ï¼
lim(x->0)(tanx-x)/(x^2sinxï¼=lim(x->0)(sinx-xcosx)/((1/2)x^2sin2x)
=lim(x->0)(sinx-xcosx)'/((1/2)x^2sin2x)'
=lim(x->0)(cosx-cosx+xsinx)/(xsin2x+x^2cos2x)
=lim(x->0)(xsinx)/(xsin2x+x^2cos2x)
=lim(x->0)(1/(2cosx+(x/sinx)cos2x))
=1/3