# Definite and Improper Integral Calculator

## Calculate definite and improper integrals step by step

The calculator will try to evaluate the definite (i.e. with bounds) integral, including improper, with steps shown.

Enter a function:

Integrate with respect to:

Enter a lower limit:

If you need -oo, type -inf.

Enter an upper limit:

If you need oo, type inf.

Please write without any differentials such as dx, dy etc.

If the calculator did not compute something or you have identified an error, or you have a suggestion/feedback, please write it in the comments below.

The Definite and Improper Integral Calculator is an online resource that allows you to easily calculate definite integrals. This advanced tool provides step-by-step solutions to help you better understand the integration process.

## How to Use the Definite and Improper Integral Calculator?

• ### Input

Enter the function you want to integrate and the upper and lower bounds of integration in the appropriate fields.

• ### Calculation

Click the "Calculate" button.

• ### Result

The calculator will quickly display the result of the integration. This will be a numerical value if the integral has a finite value. If not, the calculator will state that the integral is divergent.

## What Is a Definite Integral?

A definite integral represents the signed area between a function and the x-axis over a specified interval. The symbol for an integral is $\int$, and a definite integral is written as follows:

$$\int_a^b f(x)dx$$

Here's a detailed explanation of the components:

• $\int$ is the integral symbol.
• $a$ and $b$ are the lower and upper limits (bounds) of integration, indicating the interval on the x-axis over which the integration is performed.
• $f(x)$ is the function to integrate (the integrand). It represents a curve, the area below which is calculated.
• $dx$ is a differential, indicating that the integration is performed with respect to the variable $x$.

To compute a definite integral, one typically follows these steps:

• Find the Antiderivative: First, find the antiderivative of the function $f(x)$. This step involves finding a function $F(x)$ such that $F^{\prime}(x)=f(x)$. The antiderivative is denoted as follows:

$$F(x)=\int f(x)dx$$
• Apply the Fundamental Theorem of Calculus: The Fundamental Theorem of Calculus states that if $F(x)$ is an antiderivative of $f(x)$, then the definite integral can be evaluated as follows:

$$\int_a^b f(x)dx=F(b)-F(a)$$

This formula connects a definite integral with the difference in the values of the antiderivative at the upper and lower boundaries of integration.

The main properties and interpretations of definite integrals include the following:

• Area Under a Curve: The definite integral calculates the net area below the curve $y=f(x)$ and above the x-axis. If $f(x)$ is above the x-axis, the integral is positive and so is the area. If $f(x)$ is below the x-axis, both the integral and the area are negative.
• Accumulation of Quantity: It can also represent the total change in a quantity described by $f(x)$ over the interval $[a,b]$. For example, if $f(x)$ represents the rate of change of a quantity, then the definite integral gives the total change of that quantity over the interval.
• Signed Area: The definite integral takes into account the signed (positive or negative) area between the curve and the x-axis. This is important for understanding the direction of change represented by the integral.
• Fundamental Theorem of Calculus: The Fundamental Theorem of Calculus states that if $F(x)$ is an antiderivative of $f(x)$, i.e. $F^{\prime}(x)=f(x)$, then the definite integral of $f(x)$ from $a$ to $b$ can be evaluated as follows:

$$\int_a^b f(x)dx=F(b)-F(a)$$

It relates the definite integral to the antiderivative of the function.

## What Is an Improper Integral?

An improper integral is a type of definite integral in calculus that involves integrating a function over an infinite interval or at a point where the function becomes undefined or approaches infinity. Improper integrals are used in situations where the usual techniques for finding definite integrals do not apply due to the nature of the function or the interval of integration.

There are two main types of improper integrals:

• Improper Integral of Type 1 (infinite interval)

In this case, the integration interval extends to infinity in one or both directions. The examples of such integrals are $\int_{-\infty}^a f(x)dx$, $\int_b^{\infty}f(x)dx$, and $\int_{-\infty}^{\infty}f(x)dx$.

Let's calculate the improper integral of the function $f(x)=\frac{1}{x^2}$ from $1$ to $\infty$:

$$\int_1^{\infty}\frac{dx}{x^2}=\lim_{b\to\infty}\int_1^{b}\frac{dx}{x^2}=\lim_{b\to\infty}\left(\left.-\frac{1}{x}\right|_1^b\right)=\lim_{b\to\infty}\left(-\frac{1}{b}+\frac{1}{1}\right)=1$$

So the integral $\int_1^{\infty}\frac{dx}{x^2}$ converges to $1$.

• Improper Integral of Type 2 (discontinuities)

This type of improper integral involves integrating a function over an interval where the function has a vertical asymptote or a discontinuity. The integral can be written as follows:

$$\int_a^b f(x)dx$$

For this integral to be improper, there must exist at least one point from the interval $[a,b]$ where the integrand is undefined or has a discontinuity.

For example, let's calculate the improper integral of the function $f(x)=\frac{1}{\sqrt{x}}$ from $0$ to $1$:

$$\int_0^1 \frac{dx}{\sqrt{x}}=\lim_{a\to0^+}\int_a^1 \frac{dx}{\sqrt{x}}=\lim_{a\to0^+}\left(\left.2\sqrt{x}\right|_a^1\right)=\lim_{a\to0^+}\left(2\sqrt{1}-2\sqrt{a}\right)=2$$

This means that $\int_1^{\infty}\frac{dx}{x^2}$ converges to $2$.

But not all improper integrals converge. For example, $\int_0^1 \frac{dx}{x}$ diverges, i.e. its value is not finite.

Improper integrals are very important in various fields, such as physics and engineering, where problems involve infinite quantities or discontinuities. Their calculation often requires careful application of limits to determine convergence or divergence and obtain meaningful results.

## Why Choose Our Definite and Improper Integral Calculator?

• ### Educational Resource

Our calculator serves as an educational tool, helping users learn and understand the principles of integration.

• ### Accuracy

Our calculator uses advanced algorithms to ensure users get accurate results for definite and improper integrals.

• ### User-Friendly Interface

Designed with users in mind, our calculator has an intuitive interface that makes entering data and obtaining results easy.

• ### Support for Complex Functions

Whether you're dealing with polynomial, rational, trigonometric, exponential, or logarithmic functions, our calculator can handle them.

### FAQ

#### What is a definite integral?

A definite integral represents the signed area between a function and the x-axis over a specified interval. It is used to calculate accumulated values, areas, and changes in a quantity over a given interval. The definite integral is written as $\int_a^b f(x)dx$, where $a$ and $b$ are the lower and upper limits of integration, $f(x)$ is the function being integrated, and $dx$ indicates the integration with respect to the variable $x$.

#### What is an improper integral?

An improper integral is a type of a definite integral used in calculus to evaluate the area under a curve when traditional methods for finding definite integrals are inadequate. It usually involves integrating a function over an infinite interval or over an interval containing points where the function is undefined or infinite.

#### How to determine if an integral is improper?

An integral is determined to be improper if it falls into one of the following categories:

1. It involves integrating over an infinite interval.
2. It involves integrating a function over an interval where the function has a vertical asymptote or a discontinuity.

#### What is the difference between an improper integral and a proper integral?

The key difference lies in the nature of the bounds of integration:

• Proper Integral: The limits of integration are finite and well-defined, for example, from $a$ to $b$. The interval $[a,b]$ does not contain points that are not in the domain of $f(x)$. Traditional integration techniques apply.
• Improper Integral: The bounds of integration may involve infinity, or the interval of integration may contain points where the function is undefined or approaches infinity. Special techniques, including applying limits, are needed for evaluation.