 # Conjugate of Square Root – Definition and Examples The conjugate of a square root is a novel concept waiting to be understood and explored while delving into the mathematics and navigating through an intricate labyrinth, where every turn reveals.

By no means a stranger to mathematicians, engineers, or scientists, the notion of conjugates is fundamental in simplifying expressions and solving equations, particularly those involving square roots.

This article is a journey into understanding how conjugates of square roots work, their applications, and the elegance they bring to mathematical computations. It provides an immersive experience, whether you’re a seasoned math enthusiast or a novice keen on discovering new mathematical ideas.

## Defining Conjugate of Square Root

In mathematics, the concept of a conjugate is a fundamental tool to simplify expressions involving square roots. Specifically, when dealing with square roots, the conjugate is a method used to ‘rationalize the denominator‘ or simplify complex numbers.

For example, Suppose we have a square root expression such as √a + √b. Its conjugate is formed by changing the sign in the middle of the two terms, resulting in √a – √b.

For complex numbers, the conjugate is also an important concept. If we have a complex number like a + bi, where a and b are real numbers, and i is the square root of -1 (the imaginary unit), the conjugate of this complex number is a – bi.

The importance of the conjugate comes into play when we multiply the original expression by its conjugate. Multiplying an expression by its conjugate eliminates the square root (or the imaginary part in the case of complex numbers) due to the difference in squares’ identity, thus simplifying the expression.

## Historical Significance

The concept of a conjugate, which is the cornerstone for understanding the conjugate of a square root, is a mathematical tool with its roots firmly placed in the development of algebra and complex number theory.

The historical development of conjugates is tightly intertwined with the evolution of algebra itself. The idea to “rationalize the denominator“, or remove the square roots from the denominator of a fraction, is an old technique that can be traced back to ancient mathematicians. This process inherently uses the principle of conjugates, even if the term “conjugate” was not explicitly used.

The explicit use of the term “conjugate” and the formal concept of conjugates took form with the development of complex numbers in the 16th to 18th centuries. The Italian mathematician Gerolamo Cardano is often credited with the first systematic use of complex numbers in his work on the solutions of cubic equations, published in his 1545 bookArs Magna.”

However, the concept of the complex conjugate as we understand it today was not formalized until the 19th century, as mathematicians like Jean-Robert Argand and Carl Friedrich Gauss developed a deeper understanding of complex numbers. They recognized that every non-real complex number and its conjugate could be represented as mirror images in the Argand plane (a geometric representation of complex numbers), and these pairs of complex numbers had useful mathematical properties.

The notion of a conjugate has since become a fundamental tool in many mathematics, physics, engineering, and related fields. While it’s challenging to pinpoint the exact origin of the concept of “conjugate of a square root” itself, it’s clear that its underlying principle is closely tied to the broader historical development of algebra and complex number theory.

## Evaluating Conjugate of Square Root

Finding the conjugate of a square root term is a straightforward process. It essentially involves changing the sign between the two terms in the expression. Let’s go through the process in detail:

Consider a mathematical expression containing square roots in the form a + √b. In this expression, ‘a‘ and ‘b‘ are any real numbers. The term ‘a‘ could be a real number, another square root, or even zero.

The conjugate of this expression is formed by changing the sign between the terms ‘a‘ and ‘√b‘. So, the conjugate of ‘a + √b‘ would be ‘a – √b‘.

Similarly, if the expression were ‘a – √b‘, its conjugate would be ‘a + √b‘.

Here are the steps broken down:

### Identify the Terms

First, identify the two terms you want to find the conjugate in your expression. The expression should be ‘a + √b’ or ‘a – √b’.

### Change the Sign

Change the sign between the terms. If it’s a plus sign, change it to a minus sign. If it’s a minus sign, change it to a plus sign.

That’s it. You’ve found the conjugate of the square root expression.

As an example, consider the expression 3 + √2. The conjugate of this expression would be 3 – √2. If you have the expression 5 – √7, the conjugate would be 5 + √7.

## Properties

The conjugate of a square root has some important properties that make it an indispensable tool in mathematics. Here are some of the most significant properties:

### Elimination of Square Roots

One of the main uses of the conjugate is to eliminate square roots in an expression. Multiplying a binomial expression with a square root (such as √a + b) by its conjugate (√a – b) results in the difference of squares. This means the square root term is squared, effectively removing the square root. For example, multiplying (√a + b)(√a – b) gives us a – b².

### Simplifying Complex Numbers

The conjugate is also used to simplify complex numbers, where the square root of -1 (denoted as ‘i’) is involved. The conjugate of a complex number (a + bi) is (a – bi). If we multiply a complex number by its conjugate, we eliminate the imaginary part: (a + bi)(a – bi) = a² + b², a real number.

### Unaltered Magnitude

When we take the conjugate of a complex number, its magnitude (or absolute value) remains unchanged. The magnitude of a complex number (a + bi) is √(a² + b²), and the magnitude of its conjugate (a – bi) is also √(a² + b²).

### Reversal of Sign of Imaginary Part

The conjugate of a complex number has the same real part but an opposite sign for the imaginary part.

The conjugate of the sum (or difference) of two complex numbers equals their conjugates’ sum (or difference). In other words, if z₁ and z₂ are two complex numbers, then the conjugate of (z₁ ± z₂) is equal to the conjugate of z₁ ± the conjugate of z₂.

### Multiplication and Division

The conjugate of the product (or quotient) of two complex numbers equals the product (or quotient) of their conjugates. Thus, if z₁ and z₂ are two complex numbers, then the conjugate of (z₁ * z₂) is equal to the conjugate of z₁ * the conjugate of z₂. The same holds for division.

These properties provide a set of powerful tools that can be used to simplify mathematical expressions, solve equations, and perform complex computations.

## Applications

The concept of the conjugate of square roots, and more broadly, the conjugate of complex numbers, find widespread application across various fields of study, not only in pure mathematics but also in engineering, physics, computer science, and more. Below are some applications in different fields:

### Mathematics

In algebra, conjugates are frequently used to rationalize the denominator of fractions. The conjugate is used in complex analysis to prove fundamental results such as the Cauchy-Riemann equations. It is also used to simplify complex number expressions.

### Physics and Engineering

Complex numbers’ conjugates help analyze phase changes and amplitude in studying waves and oscillations. In electrical engineering, conjugates simplify the calculation of power in AC circuits. Quantum mechanics also utilizes complex conjugates, as the normalization condition of wave functions involves taking the complex conjugate.

### Signal Processing and Telecommunications

In digital signal processing and telecommunications, the complex conjugate is used to calculate the power spectrum of a signal and also in the correlation and convolution of signals.

### Computer Science

Complex numbers and conjugates are used in computer graphics, especially when rendering and transformations are involved. They are utilized to represent rotations, transformations, and color operations.

Additionally, the conjugate gradient method in optimization problems is another example of applying conjugates. This method is widely used for solving systems of linear equations and finding the minimum of a function.

### Control Systems

Conjugates help in analyzing the stability of control systems. The roots of the characteristic equation of a control system must be in the left half of the complex plane for the system to be stable. The roots will either be real or complex conjugate pairs.

These are just a few examples. The mathematical tool of conjugates is so versatile and powerful that it is utilized in many more areas and various ways.

## Exercise

### Example 1

#### Simplifying a Fraction

Simplify the expression 2/(3+√5).

### Solution

We use the conjugate of the denominator to rationalize it as follows:

2/(3+√5) = 2 * (3-√5) / ((3+√5) * (3-√5))

2/(3+√5) = 2 * (3-√5) / (9 – 5)

2/(3+√5) = 2 * (3-√5) / 4

2/(3+√5) = 0.5 * (3 – √5)

### Example 2

#### Simplifying a Fraction

Simplify the expression 1/(√7 – 2).

### Solution

We use the conjugate of the denominator to rationalize it as follows:

1/(√7 – 2) = (√7 + 2) / ((√7 – 2) * (√7 + 2))

1/(√7 – 2) = (√7 + 2) / (7 – 4)

1/(√7 – 2) = (√7 + 2) / 3

### Example 3

#### Multiplying a Complex Number by its Conjugate

Calculate the result of (2 + 3i) * (2 – 3i).

### Solution

This is a direct application of the conjugate:

(2 + 3i) * (2 – 3i) = 2² + (3i)²

= 4 – 9

= -5

### Example 4

#### Multiplying a Complex Number by its Conjugate

Calculate the result of (7 – 5i) * (7 + 5i).

### Solution

This is a direct application of the conjugate:

(7 – 5i) * (7 + 5i)

= 7² + (5i)²

= 49 – 25

= 24

### Example 5

#### Finding the Conjugate of a Complex Number

Find the conjugate of 6 – 2i.

### Solution

The conjugate of a complex number is found by reversing the sign of its imaginary part.

The conjugate of (6 – 2i) is:

6 + 2i

### Example 6

#### Finding the Conjugate of a Complex Number

Find the conjugate of 3 + 7i.

### Solution

The conjugate of a complex number is found by reversing the sign of its imaginary part.

Conjugate of (3 + 7i) is :

3 – 7i

### Example 7

#### Multiplying Square Roots by their Conjugates

Calculate the result of (√3 + √2) * (√3 – √2).

### Solution

This is a direct application of the conjugate:

(√3 + √2) * (√3 – √2)

= (√3)² – (√2)²

= 3 – 2

= 1

### Example 8

#### Multiplying Square Roots by their Conjugates

Calculate the result of (√5 + √7) * (√5 – √7).

### Solution

This is a direct application of the conjugate:

(√5 + √7) * (√5 – √7)

= (√5)² – (√7)²

= 5 – 7

= -2