\partial x}} වෘද්ධියට අනුරූප y{\displaystyle y} හි වෘද්ධිය ∂y{\displaystyle {\partial y}} නම්,y+∂y=f(x+∂x)−−−−−−−−−−−(2){\displaystyle y+\partial y=f(x+\partial x)-----------(2)}(2) - (1)∂y=f(x+∂x)−f(x).{\displaystyle {\partial y}=f(x+\partial x)-f(x).}limx→∂x∂y∂x=limx→∂xf(x+∂x)−f(x)∂x{\displaystyle \lim _{x\to \partial x}{\partial y \over \partial x}=\lim _{x\to \partial x}{f(x+\partial x)-f(x) \over \partial x}}limx→∂x∂y∂x=dydx=limx→∂xf(x+∂x)−f(x)∂x=f(x)−{\displaystyle \lim _{x\to \partial x}{\partial y \over \partial x}={dy \over dx}=\lim _{x\to \partial x}{f(x+\partial x)-f(x) \over \partial x}=f(x)^{-}}∂x{\displaystyle {\partial x}} ශුන්‍ය කරා එළඹෙන විට, ∂x∂y{\displaystyle {\partial x \over \partial y}} පරිමිත අගයක් ක