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JEE Main 2026 Preparation: Question Papers, Solutions, Mock Tests & Strategy Unacademy » JEE Study Material » Mathematics » Imaginary Numbers

Imaginary Numbers

In this article, we will learn about imaginary numbers, imaginary number rules, real and imaginary numbers.

Table of Content
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However, imaginary numbers, as well as the complex numbers they help define, are extremely useful. In physics, engineering, number theory, and geometry, they have a significant impact. They’re also the first step into a universe of bizarre number systems, some of which are being presented as models for the inexplicable linkages that lie beneath our physical reality.

Imaginary Numbers:

Girolamo Cardano, a great equation solver in the 1500s, was attempting to solve polynomial equations. He had no issue calculating equations like x2-8x+12=0 since it was simple to obtain two numbers with a sum of 8 and a product of 12: 2 and 6. This allowed x2-8x+12 to be factored as (x2) (x6) and expressing the polynomial as a product of two factors made the equation x2-8x+12=0 simple to solve.

However, solving equations like x2-3x+10=0 was more difficult. Finding numbers that add up to three and multiply to ten appears to be an impossible task. Because the sum of the two numbers is positive, they must both be positive. However, if 2 positive numbers add up to 3, they must both equal less than 3, implying that their product is less than 3 x 3 = 9.

What are Imaginary Numbers:

Cardano recognised that if he permitted himself to contemplate integers involving 1 (the square root of √–1), he could make it work. It was a startling revelation. The square root of a number, also known as k, is the number that yields √k when multiplied by itself. The result of squaring a real number can never be negative: for example, 3 x 3 = 9, (-1.2) x (-1.2) = 1.44, and 0 x 0 = 0. This means that no one real number could equal –1: Cardano was solving real-number equations with the number √1, although √1 isn’t a real number.

Cardano approached these non-real, or “imaginary,” numbers with caution, even dismissing the arithmetic he performed with them. He was shocked, however, to see that they followed many of the same principles as real numbers. Cardano’s hesitant use of 1 eventually led to the development of the “complex numbers,” a powerful & productive extension of real numbers.

A real part and an imagined part make up complex numbers. They take the form a + bi, with a and b both being real integers, and i=1, often known as the “imaginary unit.” Complex numbers may appear unusual at first, but we rapidly discover that we can add, subtract, multiply, and divide them just like real numbers.

Imaginary Numbers: Geometrical Interpretation

A complex number a+bi is commonly represented by a point (a, b) in the Argand plane. A complex number 1-3i, for example, represents the Argand plane point (1, -3). As a result, an imaginary number bi (which may be expressed as 0 + bi) indicates a point (0, b) on the plane, and hence a vertical axis point (imaginary axis). As a result, imaginary numbers always lie on the Argand plane’s vertical axis. A few instances follow.

If we want to use numbers to represent points in a plane, I must be a non-real number that does not belong in the Real set. In mathematics, I is defined as “one unit in the direction perpendicular to the real axis.” The point (0, 1) in the following diagram is nothing more than “i.”

As a result, the term iy in the complex number x+iy becomes a non-real number: it represents y times I or y units in the I direction. As a result, x+iy denotes a location obtained by travelling x units in the Real direction & y units in the I direction (from the origin):

Value of I:

  • It turns out that i2=1 mathematically. In other words, the square root of 1 is the value of i.

  • Just remember that i is a non-real number at this point (it lies outside the Real set).

  • One unit orthogonal to the Real direction is represented by i.

  • yi denotes y units orthogonal to the Real axis.

  • The point (x, y) is represented by x+iy, where I is the square root of 1, or i2=1.

We don’t imply that I don’t exist or that it’s a figment of our imagination when we say it’s a non-real number. We mean that i isn’t real in the sense that it doesn’t belong in the Real set. It is, nonetheless, a totally acceptable argument.

Conclusion:

The imaginary numbers are those that produce a negative result when squared. Square roots of negative numbers that have no defined value are called imaginary numbers.

The product of a real number as well as the imaginary value I is how imaginary numbers are expressed. When you square two imaginary numbers, you get a negative number. They’re also known as negative numbers’ square roots. The product of a non-zero real number and the imaginary unit i (also known as “iota”), where i = (-1) (or) i2 = -1, yields an imaginary number.

faq

Frequently asked questions

Get answers to the most common queries related to the JEE Examination Preparation.

Calculate the worth of (3i) 2.

Ans. (3i)2 = (3i) x (3i) = 9i...Read full

In terms of imaginary numbers, express the roots of the quadratic equation x² + x + 1 = 0.

Ans. We get a = 1, b = 1, and c = 1 by comparing the given quadratic equation ...Read full

Calculate the value of (a) i101 & (b) i-199

Ans. To make things easier, we apply the rule of imaginary numbers, which states that i...Read full

What can be done with imaginary numbers?

Ans. Complex numbers, often known as imaginary numbers, are used in real-world applications such as electricity and ...Read full

Why is it necessary to study imaginary numbers?

Ans. They’re quite useful in applied mathematics and physics. In quantum physics, complex numbers (the sum of ...Read full

Ans. (3i)2 = (3i) x (3i) = 9i2= 9(-1) = -9

Because i = (-1) according to the concept of imaginary numbers, i2 = -1 is the third step.

(3i)2 Equals -9.

Ans. We get a = 1, b = 1, and c = 1 by comparing the given quadratic equation to ax2 + bx + c = 0. 

Substituting these into the quadratic formula: x = (-b √ (b2 – 4ac)) / (4a) 

                                                                                       = (-1±√(12 – 4 (1)(1)) / (4 x 1) 

                                                                                       = (-1±√(1 – 4)) / 4

                                                                                       = (-1±√(-3)) / 4 

                                                                                       = (-1 i√3) / 4 

                                                                                       = (-1 i√3)

(-1 + i√3) / 4 and (-1 – i√3) / 4 are the roots, respectively.

Ans. To make things easier, we apply the rule of imaginary numbers, which states that in = ir, where n is the remainder produced by dividing n by 4.

(a) i101 = i1 = i

(b) i-199 = 1/i199 

             = 1/i3 

                    = 1/(-i) (since i3 = i2 (i))

             = (-1) (i) 

             = -(-i) 

             = i

i-199 Equals I (b) i101 = i

Ans. Complex numbers, often known as imaginary numbers, are used in real-world applications such as electricity and quadratic equations. Imaginary integers appear in equations that do not contact the x axis in quadratic planes. In advanced calculus, imaginary numbers are especially valuable.

Ans. They’re quite useful in applied mathematics and physics. In quantum physics, complex numbers (the sum of real and imaginary numbers) appear frequently. They’re handy for modelling alternating currents as well as periodic motions (like water or light waves).

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