# How to calculate integral

**Introduction**

Integration is a fundamental concept in calculus that deals with finding the area under a curve, accumulation of quantities, and many other applications in various fields such as physics, engineering, and economics. This article will guide you through the process of calculating an integral and provide insights into the different techniques you can use.

**Understanding Integrals**

An integral is used to calculate the accumulated value of a function over a given interval. The interval is usually determined by two points, one being the lower limit (a) and the other being the upper limit (b). Between these limits, the integral captures all values between them using an infinite number of infinitesimally small segments.

**There are two types of integrals:**

**1. Definite Integral –** When the lower and upper limits of integration are specified.

**2. Indefinite Integral –** When no specific limits are given.

**Basic Rules for Integration**

Before diving into integrating a function, it’s essential to understand some basic rules of integration:

**1. Integrating constants:** The integral of a constant multiplied by a function is equal to the constant multiplied by the integral of that function.

∫c * f(x) dx = c * ∫f(x) dx

**2. Power rule:** To integrate a polynomial with the form x^n, add 1 to the exponent and then divide by the new exponent.

∫x^n dx= (x^(n+1))/(n+1) + C

**3. Sum/difference rule:** The integral of a sum or difference between two functions equals the sum or difference between their individual integrals.

∫(f(x)±g(x)) dx = ∫f(x)dx ± ∫g(x)dx

**Techniques for Calculating Integrals**

Once you’re familiar with basic principles, various techniques can be employed in calculating integrals. Some popular methods are:

**1. Direct Integration:** This involves applying the basic rules of integration to find an integral.

**2. Substitution Method:** For functions that consist of a composite function, the substitution method allows you to simplify the problem by substituting a variable and applying the chain rule.

**3. Integration by Parts:** This technique is used for integrating products of functions, where you break the product into two parts and apply the rules of differentiation and integration.

**4. Partial Fractions:** This method is applicable when integrating a rational function (a fraction with polynomials as both the numerator and denominator). You decompose the function into simpler fractions.

**5. Trigonometric Substitution:** When you encounter integrals with specific forms involving quadratic terms, trigonometric substitution can be an effective solution.

**6. Table of Integrals:** In some cases, using a table of known integral formulas can help solve your problem quickly.

**Conclusion**

Calculating an integral doesn’t have to be intimidating – understanding basic rules and techniques can make solving even complex problems much more manageable. Always take a systematic approach to identify the correct technique to employ. With practice and experience, calculating integrals will become second nature!