# Second Derivative Calculator

## Calculate second derivatives step by step

This calculator will find the second derivative of any function, with steps shown. Also, it will evaluate the second derivative at the given point if needed.

Related calculators: Derivative Calculator, Logarithmic Differentiation Calculator

The Second Derivative Calculator will calculate the second derivative of a function. The step-by-step solutions it provides help deepen the knowledge of the second derivative, which provides information about the concavity of the function's curve and its inflection points.

## How to Use the Second Derivative Calculator?

### Input

Enter the function you want to differentiate twice.

### Calculation

Click the "Calculate" button.

### Result

Use the resulting second derivative to find the function's inflection points and intervals of concavity.

## What Is the Second Derivative?

The second derivative is the derivative of the first derivative of a function. It is also an important concept in calculus, which provides insight into the concavity of functions.

**Notation**

For a given function $$$f(x)$$$:

- The first derivative, denoted as $$$f^{\prime}(x)$$$, represents the rate of change of $$$f(x)$$$.
- The second derivative, denoted as $$$f^{\prime\prime}(x)$$$, represents the rate of change of $$$f^{\prime}(x)$$$: $$$f^{\prime\prime}(x)=\left(f^{\prime}(x)\right)^{\prime}$$$.

**Concavity**

The second derivative gives information about the concavity of the function's curve:

- If $$$f^{\prime\prime}(x)\gt0$$$ on some interval, the function is concave upwards on that interval.
- If $$$f^{\prime\prime}(x)\lt0$$$ on some interval, the function is concave downwards on that interval.

**Inflection Points**

An inflection point is a point where the concavity of the function changes. Mathematically, it's a point where:

- $$$f^{\prime\prime}(x)=0$$$ or $$$f^{\prime\prime}(x)$$$ is undefined.
- The sign of $$$f^{\prime\prime}(x)$$$ changes at that point.

**Example**

Suppose we are given the function $$$y=x^3+2x^2+6x+5$$$:

- First Derivative: $$$f^{\prime}(x)=3x^2+4x+6$$$.
- Second Derivative: $$$f^{\prime\prime}(x)=(3x^2+4x+6)^{\prime}=6x+4$$$.

Therefore, the function is concave upwards when $$$6x+4\gt0$$$ or $$$x\gt-\frac{2}{3}$$$, concave downwards when $$$6x+4\lt0$$$ or $$$x\lt-\frac{2}{3}$$$, and has one inflection point at $$$x=-\frac{2}{3}$$$.

## Second Derivative Test for Local Extrema

In calculus, the second derivative test is a valuable tool that helps determine the nature of the critical or stationary points of a function, in particular, whether these points are local maxima, local minima, or neither. The test uses the second derivative to determine the concavity of the function at these points.

Given a function $$$f(x)$$$ with a critical point at $$$x=c$$$:

- If $$$f^{\prime\prime}(x)\gt0$$$, then $$$x=c$$$ is a local minimum because the function $$$f(x)$$$ is concave upwards at this point. This means that, in a small neighborhood of $$$x=c$$$, the function values are greater than $$$f(c)$$$.
- If $$$f^{\prime\prime}(x)\lt0$$$, then $$$x=c$$$ is a local maximum because the function $$$f(x)$$$ is concave downwards at this point. This means that, in a small neighborhood of $$$x=c$$$, the function values are less than $$$f(c)$$$.
- If $$$f^{\prime\prime}(x)=0$$$ or $$$f^{\prime\prime}(x)$$$ does not exist, the second derivative test is inconclusive. The point can be an inflection point, a local maximum, a local minimum, or none of the above. In such cases, further analysis or other methods are needed to determine the nature of the critical point.

## Why Choose Our Second Derivative Calculator?

### Precision

The calculator provides high accuracy, removing the possibility of human errors that can occur with manual calculations.

### Speed

Our tool produces instant results. No more lengthy manual calculations. You save your time.

### Intuitive Design

Navigating our calculator is a breeze thanks to its user-friendly interface, which is designed to simplify the entire process.

### Versatility

Our calculator can handle a wide range of functions, from trigonometric to logarithmic.

### FAQ

#### What is the second derivative?

The second derivative of a function is the rate of change of its first derivative. For a function $$$f(x)$$$, its second derivative is denoted by $$$f^{\prime\prime}(x)$$$.

#### When is the second derivative positive?

If the second derivative $$$f^{\prime\prime}(x)$$$ is positive at some point or on some interval, the function $$$f(x)$$$ is concave upwards at that point or on that interval.

#### What is the second derivative test used for?

The second derivative test is a method used to determine the nature of critical points (where the first derivative is zero or undefined) of a function. If $$$f^{\prime\prime}(c)\gt0$$$, the function has a local minimum at $$$x=c$$$. If $$$f^{\prime\prime}(c)\lt0$$$, there is a local maximum at $$$x=c$$$. If $$$f^{\prime\prime}(c)=0$$$, the test is inconclusive, and other methods are needed to determine the nature of the critical point.

#### What does the Second Derivative Calculator do?

The Second Derivative Calculator is a tool that computes the second derivative of a function. It provides fast and accurate results without the need for manual calculations.