Imaginary Numbers (2024)

An Imaginary Number,when squared, gives a negative result.
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Try

Let's try squaring some numbers to see if we can get a negative result:

No luck! Always positive, or zero.

It seems like we cannot multiply a number by itself to get a negative answer ...

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... but imagine that there is such a number (call it i for imaginary) that could do this:

i × i = −1

Would it be useful, and what could we do with it?

Well, by taking the square root of both sides we get this:

Imaginary Numbers (3)
Which means that i is the answer to the square root of −1.

Which is actually very useful because ...

... by simply accepting that i exists we can solve things
that need the square root of a negative number.

Let us have a go:

Example: What is the square root of −9 ?

√(−9)= √(9 × −1)

= √(9) × √(−1)

= 3 × √(−1)

= 3i

(see how to simplify square roots)

Hey! that was interesting! The square root of −9 is simply the square root of +9, times i.

In general:

√(−x) = i√x

So long as we keep that little "i" there to remind us that we still
need to multiply by √−1 we are safe to continue with our solution!

Using i

Example: What is (5i)2 ?

(5i)2= 5i × 5i

= 5× 5× i × i

= 25 × i2

= 25 × −1

= −25

Interesting! We used an imaginary number (5i) and ended up with a real solution (−25).

Imaginary numbers can help us solve some equations:

Example: Solve x2 + 1 = 0

Using Real Numbers there is no solution, but now we can solve it!

Subtract 1 from both sides:

x2 = −1

Take the square root of both sides:

x = ± √(−1)

x = ± i

Answer: x = −i or +i

Check:

  • (−i)2 + 1 = (−i)(−i) + 1 = +i2 + 1 = −1 + 1 = 0
  • (+i)2 +1 = (+i)(+i) +1 = +i2 +1 = −1 + 1 = 0

Imaginary Numbers (4)

Unit Imaginary Number

The square root of minus one √(−1) is the "unit" Imaginary Number, the equivalent of 1 for Real Numbers.

In mathematics the symbol for√(−1) is i for imaginary.

Can you take the square root of −1?
Well i can!

But in electronics they use j (because "i" already means current, and the next letter after i is j).

Examples of Imaginary Numbers

i12.38i−i3i/40.01iπi

Imaginary Numbers are not "Imaginary"

Imaginary Numbers were once thought to be impossible, and so they were called "Imaginary" (to make fun of them).

But then people researched them more and discovered they were actually useful and important because they filled a gap in mathematics ... but the "imaginary" name has stuck.

And that is also how the name "Real Numbers" came about (real is not imaginary).

Imaginary Numbers are Useful

Imaginary Numbers (5)

Complex Numbers

Imaginary numbers become most useful when combined with real numbers to make complex numbers like 3+5i or 6−4i

Spectrum Analyzer

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Those cool displays you see when music is playing? Yep, Complex Numbers are used to calculate them! Using something called "Fourier Transforms".

In fact many clever things can be done with sound using Complex Numbers, like filtering out sounds, hearing whispers in a crowd and so on.

It is part of a subject called "Signal Processing".

Electricity

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AC (Alternating Current) Electricity changes between positive and negative in a sine wave.

When we combine two AC currents they may not match properly, and it can be very hard to figure out the new current.

But using complex numbers makes it a lot easier to do the calculations.

And the result may have "Imaginary" current, but it can still hurt you!

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Mandelbrot Set

The beautiful Mandelbrot Set (part of it is pictured here) is based on Complex Numbers.

Quadratic Equation

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The Quadratic Equation, which has many uses,
can give results that include imaginary numbers

Also Science, Quantum mechanics and Relativity use complex numbers.

Interesting Property

The Unit Imaginary Number, i, has an interesting property. It "cycles" through 4 different values each time we multiply:

1 × i= i
i × i= −1
−1 × i= −i
i × i= 1
Back to 1 again!
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So we have this:

i = √−1i2 = −1i3 = −√−1i4 = +1
i5 = √−1i6 = −1...etc

Example What is i10 ?

i10= i4 × i4 × i2

= 1 × 1 × −1

= −1

And that leads us into another topic, the complex plane:

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Conclusion

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The unit imaginary number, i, equals the square root of minus 1

Imaginary Numbers are not "imaginary", they really exist and have many uses.

Imaginary Numbers (2024)

FAQs

What is imaginary number short answer? ›

An imaginary number is a real number multiplied by the imaginary unit i, which is defined by its property i2 = −1. The square of an imaginary number bi is −b2. For example, 5i is an imaginary number, and its square is −25. By definition, zero is considered to be both real and imaginary.

Are imaginary numbers actually useful? ›

Imaginary numbers, also called complex numbers, are used in real-life applications, such as electricity, as well as quadratic equations. In quadratic planes, imaginary numbers show up in equations that don't touch the x axis. Imaginary numbers become particularly useful in advanced calculus.

What is 2i equal? ›

2i is an imaginary number because it has the form 'bi' Remember, 'i' is the imaginary unit and is equal to the square root of -1. Even though 'i' is NOT a variable, we can multiply it as if it were. So i • i gives us i2. Squaring √ (-1) cancels out the square root, leaving us with just -1.

Is 0 real or imaginary? ›

Zero is considered both a real number and an imaginary number. When the broad sense is used, the term purely imaginary number (or pure imaginary number) may be used for an imaginary number in the strict sense.

Is 0 a real number? ›

Zero is considered to be both a real and an imaginary number. As we know, imaginary numbers are the square root of non-positive real numbers. And since 0 is also a non-positive number, therefore it fulfils the criteria of the imaginary number.

Is 17 a complex number? ›

There is no imaginary part. In other words, the imaginary part is 0. We can think of 17 as 17 + 0i. In fact all real numbers can be thought of as complex numbers which have zero imaginary part.

Is 1 a real number? ›

The type of number we normally use, such as 1, 15.82, −0.1, 3/4, etc. Positive or negative, large or small, whole numbers, fractions or decimal numbers are all Real Numbers. They are called "Real Numbers" because they are not Imaginary Numbers.

What is the imaginary number of 1? ›

The square root of minus one √(−1) is the "unit" Imaginary Number, the equivalent of 1 for Real Numbers. In mathematics the symbol for √(−1) is i for imaginary.

What career uses imaginary numbers? ›

Physics (e.g., quantum mechanics, relativity, other subfields) makes use of imaginary numbers. "Complex analysis" (i.e., calculus that includes imaginary numbers) can also be used to evaluate difficult integrals and to perform other mathematical tricks.

Why is i to the power of i real? ›

If you are familiar with complex numbers, the “imaginary” number i has the property that the square of i is -1. It is a rather curious fact that i raised to the i-th power is actually a real number! In fact, its value is approximately 0.20788.

What are some jobs that use imaginary numbers? ›

  • Business.
  • Computers & Technology.
  • Criminal Justice.
  • Education.
  • Engineering & Science.
  • Humanities.
  • Nursing & Healthcare.
  • Psychology.
20 Oct 2021

Why is 1089 special? ›

It is a square number (33 squared), a nonagonal number, a 32-gonal number, a 364-gonal number, and a centered octagonal number. 1089 is the first reverse-divisible number. The next is 2178 (= 1089 × 2 = 8712/4), and they are the only four-digit numbers that divide their reverse.

What is the i in math? ›

The imaginary unit or unit imaginary number (i) is a solution to the quadratic equation . Although there is no real number with this property, i can be used to extend the real numbers to what are called complex numbers, using addition and multiplication.

What is i3 equal to? ›

Answer and Explanation: The value of i3 is -i. We can determine this by multiplying i, or √−1 , by itself three times. We see that i3 = -i.

Is 5 real or imaginary? ›

5 is the real number and i is the imaginary unit. When this number 5i is squared, we will get the negative result as -25.

Who is the father of zero? ›

About 773 AD the mathematician Mohammed ibn-Musa al-Khowarizmi was the first to work on equations that were equal to zero (now known as algebra), though he called it 'sifr'. By the ninth century the zero was part of the Arabic numeral system in a similar shape to the present day oval we now use.

Is Pi an imaginary number? ›

π is not an imaginary number, which are numbers in the form of xi, x∈R.

What is R * in math? ›

Meaning of R * : In the number system, R * is the set of all non-zero real numbers, which form the group under the multiplication operation. In functions, R * is the reflexive-transitive closure of binary relation R in the set.

Is infinity a real number? ›

Infinity is a "real" and useful concept. However, infinity is not a member of the mathematically defined set of "real numbers" and, therefore, it is not a number on the real number line.

What is r in math? ›

In mathematics, the alphabet R denotes the set of real numbers. The real numbers are classified as: Rational numbers: These numbers can be written as a ratio of two integers numbers, provided, a non-zero denominator.

Is 3d a complex number? ›

A system of commutative hypercomplex numbers of the form w=x+hy+kz are introduced in 3 dimensions, the variables x, y and z being real numbers. The multiplication rules for the complex units h, k are h^2=k, k^2=h, hk=1.

Is 0 a complex number? ›

Therefore we can say that yes, zero is a complex number. So, the correct answer is “YES”. Note: Each and every possible number in mathematics is a complex number, because a complex number is the parent branch of all other number groups like there are two branches of complex numbers real numbers and imaginary numbers.

Is 9i a real number? ›

1 Answer. 5 is the real part, and 9i is the imaginary part.

What does Z mean in math? ›

List of Mathematical Symbols • R = real numbers, Z = integers, N=natural numbers, Q = rational numbers, P = irrational numbers.

Is Pi a whole number? ›

π=3.141592......... Thus it is infinite, since it has a decimal it cannot be whole, natural or an integers, it can also not be a rational number because it is believed to be an infinite number and rational numbers are said to be infinite. The number pi is therefore an irrational number.

Is zero a whole number? ›

Whole numbers include all natural numbers and zero. Natural numbers are generally used for counting objects or things. The set of whole numbers is, W = {0,1,2,3,…}.

Is 0.5 an imaginary number? ›

All real numbers (like 0.5, √3, π, ...) are complex numbers, as are all imaginary numbers (like 0.5i, i√3, πi, ...). Additionally, this covers basic addition and subtraction of complex numbers as an extension of combining like terms.

Is 7 an imaginary number? ›

No , in fact , it isn't even a real number!

What is a power of 5? ›

In arithmetic and algebra, the fifth power or sursolid of a number n is the result of multiplying five instances of n together: n5 = n × n × n × n × n. Fifth powers are also formed by multiplying a number by its fourth power, or the square of a number by its cube.

What skill is good with numbers? ›

Numeracy is the ability to recognise and apply maths concepts in all areas of life. Numeracy skills involve understanding numbers, counting, solving number problems, measuring, estimating, sorting, noticing patterns, adding and subtracting numbers, and so on.

What are numbers in reality? ›

The “real numbers” are some of our most familiar mathematical objects: They are all the numbers that can be represented in decimal notation, like 5, 8.2, -13.712, 0, 10.33333… and \pi \approx 3.141592….

What is the rule of i? ›

"I before E, except after C" is a mnemonic rule of thumb for English spelling. If one is unsure whether a word is spelled with the digraph ei or ie, the rhyme suggests that the correct order is ie unless the preceding letter is c, in which case it may be ei.

What number family is the largest? ›

So, the correct answer is 'Compositae'

Where did imaginary numbers come from? ›

The earliest traces of imaginary numbers find themselves in Italy, nestled inside a cubic equation. During the early 1500s, the dividing line between university mathematics and informal mathematics shrunk, and there was a rapid development in algebra [8].

What jobs dont use numbers? ›

20 high-paying jobs that don't require math
  • Compliance manager.
  • Marketing manager.
  • Music teacher.
  • Historian.
  • Recruitment manager.
  • Art director.
  • Web developer.
  • Documentation manager.

What jobs use maths everyday? ›

Examples of the many jobs that use math and require math-based degrees include accountants, engineers, scientific researchers, architects and drafters.

How do you get rid of imaginary numbers in math? ›

To eliminate the imaginary component from a complex number, multiply by its complex conjugate. This is how division with complex numbers is done. The numerator and denominator is multiplied by the complex conjugate of the denominator.

How do you do operations with imaginary numbers? ›

To add two complex numbers , add the real part to the real part and the imaginary part to the imaginary part. To subtract two complex numbers, subtract the real part from the real part and the imaginary part from the imaginary part. To multiply two complex numbers, use the FOIL method and combine like terms .

How do you simplify an imaginary number problem? ›

A simple shortcut to simplify an imaginary unit raised to a power is to divide the power by 4 and then raise the imaginary unit to the power of the reminder. For example: to simplify j23, first divide 23 by 4. 23/4 = 5 remainder 3.

Why do mathematicians use imaginary numbers? ›

Why do we have imaginary numbers anyway? The answer is simple. The imaginary unit i allows us to find solutions to many equations that do not have real number solutions.

Why is imaginary number so called? ›

(The name dates back to when they were first introduced, before their existence was really understood. At that point in time, people were imagining what it would be like to have a number system that contained square roots of negative numbers, hence the name "imaginary".

What is the square of √ 1? ›

Square Root From 1 to 50
NumberSquare Root Value
11
21.414
31.732
42
46 more rows
9 Jun 2020

What is the imaginary number rule? ›

Imaginary numbers are the numbers when squared it gives the negative result. In other words, imaginary numbers are defined as the square root of the negative numbers where it does not have a definite value.

What kind of math uses imaginary numbers? ›

Imaginary numbers, also called complex numbers, are used in real-life applications, such as electricity, as well as quadratic equations. In quadratic planes, imaginary numbers show up in equations that don't touch the x axis. Imaginary numbers become particularly useful in advanced calculus.

Can you add 2 imaginary numbers? ›

To add or subtract two complex numbers, just add or subtract the corresponding real and imaginary parts. For instance, the sum of 5 + 3i and 4 + 2i is 9 + 5i. For another, the sum of 3 + i and –1 + 2i is 2 + 3i.

Can imaginary numbers cancel out? ›

Well, the same thing happens here when you multiply the complex number in the denominator by its complex conjugate: the imaginary number middle terms will cancel each other out!

Is the square root of 17 a real number? ›

Because it cannot be expressed in the form p/q, the square root of 17 is an irrational number.

What does 2 imaginary solutions mean? ›

You may have used the quadratic formula before, but this time we are working with quadratic equations with two imaginary solutions. All this means is that there are negative numbers under the radical that have to be converted into imaginary numbers.

What is 1 as an imaginary number? ›

Unit Imaginary Number

The square root of minus one √(−1) is the "unit" Imaginary Number, the equivalent of 1 for Real Numbers. In mathematics the symbol for √(−1) is i for imaginary.

What does 3i mean in math? ›

Imaginary Numbers

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