lim(x->0) f(x)/g(x),應用羅必達法則=lim(x->0) sin(1-cosx)^2/(x^4+x^5)=lim(x->0) cos(1-cosx)^2* 2(1-cosx)*sinx/(4x^3+5x^4)=lim(x->0) 2(1-cosx)/(4x^2+5x^3)*sinx/x=lim(x->0) 2(1-cosx)/(4x^2+5x^3)=lim(x->0...你第一個=lim(x->0) sin(1-cosx)^2/(x^4+x^5) 上面還少乘一個（1-cosx）的求導哦，是喔lim(x->0) f(x)/g(x),應用羅必達法則=lim(x->0) sin(1-cosx)^2*sinx/(x^4+x^5)=lim(x->0) sin(1-cosx)^2 /(x^3+x^4), 再用法則=lim(x->0) cos(1-cosx)^2* 2(1-cosx)*sinx/(3x^2+4x^3)=lim(x->0) 2(1-cosx)/(3x+4x^2)=lim(x->0) 2sinx/(3+8x)=0這樣得話得選B了