对于一阶的,在“同一点”,两个值是互为倒数的。
例如:y=f(x)=sin(x),x=g(y)=arcsin(y)f′(x)=cos(x)g′(y)=dxdy=1dydx=1cos(x)=⟶同一点1cos(x)=1−y2例如:y=f(x)=sin(x) , x=g(y)=arcsin(y) \\
f'(x)=cos(x)\\
g'(y)=\frac{dx}{dy}=\frac{1}{\frac{dy}{dx}}=\frac{1}{cos(x)}=\stackrel{同一点}{\longrightarrow}\frac{1}{ cos(x) =\sqrt[]{1-y^2}}\\
例如:y=f(x)=sin(x),x=g(y)=arcsin(y)f′(x)=cos(x)g′(y)=dydx=dxdy1=cos(x)1=⟶同一点cos(x)=1−y21
g′(y)=1f′(x)g′′(y)=d[g′(y)]dy=d[1f′(x)]dy=d[1f′(x)]dxdydx=−f′′(x)f′(x)3
g'(y)=\frac{1}{f'(x)}\\
g''(y)=\frac{d \left[ g'(y) \right] }{dy} =\frac{d \left[ \frac{1}{f'(x)} \right] }{dy} =\frac{ \frac{ d\left[ \frac{1}{f'(x)} \right] }{dx} }{ \frac{dy}{dx} }=-\frac{f''(x)}{{f'(x)}^3} \\
g′(y)=f′(x)1g′′(y)=dyd[g′(y)]=dyd[f′(x)1]=dxdydxd[f′(x)1]=−f′(x)3f′′(x)