# Implicit differentiation

## The Fundamentals of Implicit Differentiation: How to Differentiate Implicit Functions

Implicit functions, also known as equations with two unknown variables, x and y, can be challenging to solve for y in terms of x using standard differentiation methods. This is where implicit differentiation comes into play.

Implicit differentiation is a technique that enables us to find the derivative of y with respect to x (dy/dx) without having to isolate y. It is a valuable tool for defining the slope and curvature of curves represented by implicit functions. Additionally, implicit differentiation can be used to construct equations for tangents and normal lines of these curves.

## The Process of Implicit Differentiation

To perform implicit differentiation, we use a modified version of the chain rule for equations in the form of x + y = a, assuming that y is a function of x. The process involves differentiating both sides of the equation with respect to x. For terms involving y, we multiply by dy/dx. Finally, we can solve for dy/dx. Let's look at an example to better understand this concept.

Example: Find the derivative of a circle defined by the equation (x + y)^2 = 9.

Solution: We differentiate each part of the equation with respect to x. However, for the y term, we also multiply by dy/dx. Hence, we get (x + y)^2 * (1 + dy/dx) = 0. Solving for dy/dx, we get dy/dx = - x / (y + x).

## Implicit Differentiation of Higher Orders

For higher order differentiation, we follow the same process with a slight modification. To find the second derivative, we differentiate the first derivative, and for the third derivative, we differentiate the second derivative, and so on. We can use the formula dyn/dxn = [dy/dx * dy/dxn-1 + dn-1y/dxn-1 * dn-1y/dx] / [dy/dxn-1]^3 to generalize this process, where n represents the order of the derivative needed.

## Finding Equations for Tangents and Normals

We can use implicit differentiation to determine the equation of the tangent of a curve. The formula y - y1 = a (x - x1) can be utilized for this purpose, where (x1, y1) are the coordinates of the point of tangency, and a is the slope or derivative of the curve. Similarly, we can use the formula y - y1 = (-1/a) (x - x1) for finding the equation of the normal, where a represents the slope of the tangent.

Example: Find the equation of the tangent and normal to the curve defined by (x + y)^2 = 9 at the point where x = 1.

Solution: To find the point of tangency, we substitute x = 1 into the equation and solve for y, getting y = 2 or y = -2. We also need the slope of the tangent, which we can find using implicit differentiation. So, dy/dx = -1/2 at x = 1. Substituting these values into the equation for the tangent, we get y - 2 = (-1/2) (x - 1) or y + 2 = 2 (x - 1). Similarly, for the normal, we get y - 2 = (-2) (x - 1) or y + 2 = -1 (x - 1).

## Key Takeaways

• Implicit differentiation is a method for finding the derivative of an implicit function without having to solve for y in terms of x.
• All terms in the equation are differentiated, and the y term is multiplied by dy/dx.
• For higher order differentiation, we can use a formula to find the nth derivative.
• We can use implicit differentiation to find equations for tangents and normals of curves defined by implicit functions.

## Understanding Implicit Differentiation: A Valuable Tool for Solving Equations

Implicit differentiation is a method used to find the derivative of an implicit function, where both x and y are variables and are not isolated on one side of the equation. This technique is especially useful when solving equations where y is a function of x, not just a constant.

But when should you utilize implicit differentiation? It is most helpful when dealing with implicit functions, where it may be difficult or impossible to solve for y explicitly. In these cases, implicit differentiation can simplify the process and provide a quick and accurate solution.

So, how do we find dy/dx using this method? First, we differentiate the term with y and then rearrange the equation to isolate the dy/dx term on one side. This will give us the derivative expression for the function, allowing us to find the slope or rate of change at any given point.

Now, why is implicit differentiation a valuable tool? As mentioned earlier, it eliminates the need to solve for y before differentiating. This can save time and effort, particularly when dealing with complex equations.

Now armed with the basics of implicit differentiation, you can confidently tackle tricky equations. No longer will you have to struggle with isolating variables or solving for y. Happy differentiating!