Summary of Partial Derivatives

Essential Concepts

  • A partial derivative is a derivative involving a function of more than one independent variable.
  • To calculate a partial derivative with respect to a given variable, treat all the other variables as constants and use the usual differentiation rules.
  • Higher-order partial derivatives can be calculated in the same way as higher-order derivatives.

Key Equations

  • Partial derivative of [latex]f[/latex] with respect to [latex]x[/latex]
    [latex]\frac{\partial f}{\partial x}=\underset{h \to{0}}{\lim} \frac{f(x+h,y)-f(x,y)}{h}[/latex]
  • Partial derivative of [latex]f[/latex] with respect to [latex]y[/latex]
    [latex]\frac{\partial f}{\partial y}=\underset{k \to{0}}{\lim} \frac{f(x,y+k)-f(x,y)}{k}[/latex]

Glossary

higher-order partial derivatives
second-order or higher partial derivatives, regardless of whether they are mixed partial derivatives
mixed partial derivatives
second-order or higher partial derivatives, in which at least two of the differentiations are with respect to different variables
partial derivative
a derivative of a function of more than one independent variable in which all the variables but one are held constant
partial differential equation
an equation that involves an unknown function of more than one independent variable and one or more of its partial derivatives