Implicit differentiation

What is Implicit differentiation?

Implicit differentiation is a technique that allows us to differentiate equations that cannot be expressed in the form $y = f(x)$. It is based on the fact that the derivative of a function is equal to the derivative of the dependent variable with respect to the independent variable, multiplied by the derivative of the independent variable with respect to itself.

Here is an example of implicit differentiation using KaTeX syntax:

Let's say we want to differentiate the equation $x^2 + y^2 = 9$. This equation cannot be written in the form $y = f(x)$, so we cannot use the standard rules of calculus to differentiate it. Instead, we can use implicit differentiation to find the derivative of $y$ with respect to $x$.

We start by differentiating both sides of the equation with respect to $x$:

$$\frac{d}{dx} (x^2 + y^2) = \frac{d}{dx} 9$$

Using the chain rule, we can write the derivative of the left-hand side as:

$$2x + 2y \cdot \frac{dy}{dx} = 0$$

We can then solve for $\frac{dy}{dx}$:

$$\frac{dy}{dx} = -\frac{2x}{2y} = -\frac{x}{y}$$

So, the derivative of $y$ with respect to $x$ is $-\frac{x}{y}$.

This is an example of how implicit differentiation can be used to find the derivative of a function that is not explicitly defined in terms of $x$ and $y$. It is a useful technique when we are given an equation that cannot be written in the form $y = f(x)$ and we want to find the derivative of one of the variables with respect to the other.