# Imaginary Numbers – Definition With Examples

6 minutes read

Created: December 16, 2023

Last updated: January 2, 2024

Imagine a world where the boundaries of mathematics are expanded beyond what’s visible. At Brighterly, we believe that the beauty of math isn’t limited to just numbers we see and use daily. Beyond these known quantities lies a fascinating realm of imaginary numbers. While they might seem like figures from a fairy tale, these numbers have real-world applications and serve as a cornerstone in many advanced areas of science and engineering. Dive in with us as we unravel the mystique of imaginary numbers, making it as bright and clear as the world of real numbers you’re already familiar with.

## What Are Imaginary Numbers?

Have you ever tried to think about a square root of a negative number? In the world of real numbers, it doesn’t exist. Enter, the imaginary numbers! Just like the name suggests, they might sound made-up or fictional, but they play a vital role in advanced mathematics, engineering, and physics.

## Definition of Imaginary Numbers

Imaginary numbers are numbers that can be written as a real number multiplied by the imaginary unit i, which is defined by the property $i²=−1$. Simply put, the square root of -1 is termed as ‘i’. So, if we talk about the square root of -4, it’s represented as $i²$. These numbers exist outside the realm of the real number line we’re accustomed to.

## Definition of Real Numbers

In contrast, real numbers are numbers that can be found on the number line. This includes all the numbers we deal with daily: whole numbers, fractions, decimals, positives, negatives, and even zero. They’re termed ‘real’ because they represent quantities that we can touch, measure, and observe.

## Properties of Imaginary Numbers

- Square Property: As stated, $i²=−1$
- Power Cycling: The powers of i cycle in a pattern: $i,i²,i³,i⁴,$ which are equivalent to $i,−1,−i,1$ respectively.
- Addition & Subtraction: Imaginary numbers can be added or subtracted in the same way as like terms. E.g., $3i+4i=7i$.

## Properties of Real Numbers

- Ordering: Real numbers can be ordered on a number line.
- Arithmetic Operations: Addition, subtraction, multiplication, and division (except by zero) are always possible and will result in a real number.
- Absolute Value: Every real number has a non-negative absolute value.

## Difference Between Imaginary and Real Numbers

The most fundamental difference between the two is their placement. While real numbers reside on the number line, imaginary numbers are off this chart, existing in a different dimension. You can think of real numbers as the x-axis and imaginary numbers as the y-axis on the complex plane.

## Equations Involving Imaginary Numbers

When equations have no solution within the real number system, often, the solution lies in the realm of imaginary numbers.

## Writing Equations Involving Imaginary Numbers

To represent equations with imaginary solutions, we use the imaginary unit i. For example, the equation $x²+1=0$ has solutions $x=i$ and $x=−i$.

## Solving Equations with Imaginary Numbers

To solve, factorize or use the quadratic formula as usual. If you find yourself taking the square root of a negative number, remember that’s an opportunity for i to come into play.

## Practice Problems on Imaginary Numbers

- Solve: $x²+4=0$
- If z=3+4i, find $z²$.
- Solve: $2x²+8=0$

## Conclusion

Through our journey at Brighterly, we’ve ventured beyond the visible horizon of real numbers and explored the enigmatic world of imaginary numbers. We learned that math isn’t just about counting tangible objects; it’s also about understanding concepts that help us decode complex problems in various disciplines. As with all things at Brighterly, our aim is to illuminate the unknown and make learning an adventurous expedition. So the next time you encounter a seemingly ‘imaginary’ concept, remember, there’s always a brighter side to understanding it!

## Frequently Asked Questions on Imaginary Numbers

### What are the applications of imaginary numbers?

While the name might suggest they’re fictitious, imaginary numbers have pivotal roles in real-world scenarios. They are instrumental in fields like electrical engineering, where they help analyze alternating current circuits. In physics, wave mechanics and quantum mechanics utilize them. Additionally, they’re essential in complex analysis, fluid dynamics, and various areas in mathematics.

#### Can imaginary numbers be graphed?

Absolutely! Imaginary numbers can be visualized using a complex plane. On this plane, the horizontal axis (x-axis) represents real numbers, and the vertical axis (y-axis) represents imaginary numbers. It’s similar to a coordinate plane, but with the vertical values being multiples of i.

### Why is ‘i’ called the imaginary unit?

The term “imaginary” was historically used to describe numbers that couldn’t be visualized on the real number line. The imaginary unit i represents the square root of -1, a value that doesn’t have a ‘real’ counterpart. It’s a foundational concept that allows us to understand and work with complex numbers in mathematics and various applications.

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