{\displaystyle {\begin{aligned}\delta y&=uv+u\delta v+v\delta u+\delta u\delta v-uv\\&=u\delta v+v\delta u+\delta u\delta v\end{aligned}}}δx{\displaystyle \delta x} වලින් බෙදු විට,δyδx=uδvδx+vδuδx+δuδvδxlimδx→0δyδx=limδx→0(uδvδx+vδuδx+δuδvδx)=ulimδx→0δvδx+vlimδx→0δuδx+limδx→0δuδvδx{\displaystyle {\begin{aligned}{\frac {\delta y}{\delta x}}&=u{\frac {\delta v}{\delta x}}+v{\frac {\delta u}{\delta x}}+{\frac {\delta u\delta v}{\delta x}}\\\lim \limits _{\delta x\to 0}{\frac {\delta y}{\delta x}}&=\lim \limits _{\delta x\to 0}\left(u{\frac {\delta v}{\delta x}}+v{\frac {\delta u}{\delta x}}+{\frac {\delta u\delta v}{\delta x}}\right)\\&=u\lim \limits _{\delta x\to 0}{\frac {\delta v}{\delta x}}+v\lim \limits _{\delta x\to 0}{\frac {\delta u}{\d