洛必达法则原式 = lim(x->+0) [tan(sinx)]^(1/2) * cosx / { - [sin(tanx)]^(1/2) * sec²x } = lim(x->+0) x^(1/2) cos³x / [ -x^(1/2)] = -1利用 x->+0, tan(sinx) ~ sinx ~ x, sin(tanx) ~ tanx ~ x
