Implicit differentiation

Definition

Implicit differentiation is a technique used in calculus to find the derivative of a function defined implicitly, rather than explicitly as $y = f(x)$. In cases where it’s difficult or impossible to solve for one variable in terms of another, implicit differentiation allows us to differentiate both sides of an equation with respect to the independent variable, applying the chain rule appropriately to account for dependent variables.

5 Must Know Facts For Your Next Test

1. Implicit differentiation is especially useful when dealing with equations that define $y$ implicitly, like $x^2 + y^2 = 1$, which represents a circle.
2. To perform implicit differentiation, you treat $y$ as a function of $x$ and apply the derivative operator to both sides of the equation, using the chain rule for $y$ terms.
3. After differentiating, you often solve for $rac{dy}{dx}$ to express the slope of the tangent line at any point on the curve defined by the implicit equation.
4. This method can yield results even when it is not straightforward to isolate $y$ in an explicit form, making it a powerful tool for calculus problems.
5. Implicit differentiation can also be applied to functions of multiple variables, allowing for more complex relationships between variables.

Review Questions

• How does implicit differentiation differ from explicit differentiation, and why might one choose to use it?
  • Implicit differentiation differs from explicit differentiation in that it allows for finding derivatives of functions defined by equations where one variable cannot be easily isolated. For instance, when dealing with complex shapes or curves represented by equations like $x^2 + y^2 = r^2$, isolating $y$ can be challenging. Using implicit differentiation simplifies this process by allowing you to differentiate both sides directly while applying the chain rule, making it particularly useful in cases where direct differentiation isn't feasible.
• Describe how you would apply implicit differentiation to find $rac{dy}{dx}$ for the equation $x^3 + y^3 = 6xy$.
  • To apply implicit differentiation to the equation $x^3 + y^3 = 6xy$, first differentiate each term with respect to $x$. The left-hand side gives $rac{d}{dx}(x^3) + rac{d}{dx}(y^3) = 3x^2 + 3y^2 rac{dy}{dx}$. The right-hand side differentiates as $rac{d}{dx}(6xy) = 6(y + xrac{dy}{dx})$. Setting both sides equal leads to an equation containing $rac{dy}{dx}$ terms that can be isolated and solved for $rac{dy}{dx}$.
• Evaluate how implicit differentiation aids in understanding multivariable functions and their relationships within economic models.
  • Implicit differentiation plays a crucial role in understanding multivariable functions within economic models, especially when these models involve complex relationships between variables that are interdependent. For example, in models where supply and demand are expressed through implicit equations, understanding how changes in one variable affect another becomes essential. By applying implicit differentiation, economists can derive important insights such as elasticity and marginal effects without needing explicit forms for every variable involved. This approach ultimately enhances decision-making based on how closely interrelated economic factors are.

Related terms

chain rule: A fundamental rule in calculus used to differentiate composite functions, stating that the derivative of a function is the product of the derivative of the outer function and the derivative of the inner function.

partial derivatives: Derivatives of functions with multiple variables taken with respect to one variable while keeping other variables constant, providing insights into how a function changes in different directions.

total derivative: The derivative of a multivariable function that accounts for changes in all input variables, providing a complete picture of how the function behaves with respect to its entire input space.