imaginary unit

(noun)

A complex number, usually denoted with i, that is defined as i^2 = -1

Related Terms

Examples of imaginary unit in the following topics:

  • Addition, Subtraction, and Multiplication

    • Complex numbers are added by adding the real and imaginary parts; multiplication follows the rule $i^2=-1$.
    • Complex numbers are added by adding the real and imaginary parts of the summands.
    • The preceding definition of multiplication of general complex numbers follows naturally from this fundamental property of the imaginary unit.
    • = $(ac - bd) + (bc + ad)i$ (by the fundamental property of the imaginary unit)

  • Introduction to Complex Numbers

    • A complex number has the form $a+bi$, where $a$ and $b$ are real numbers and $i$ is the imaginary unit.
    • A complex number is a number that can be put in the form $a+bi$ where $a$ and $b$ are real numbers and $i$ is called the imaginary unit, where $i^2=-1$.
    • In this expression, $a$ is called the real part and $b$ the imaginary part of the complex number.
    • To indicate that the imaginary part of $4-5i$ is $-5$, we would write $\text{Im}\{4-5i\} = -5$.
    • A complex number whose real part is zero is said to be purely imaginary, whereas a complex number whose imaginary part is zero is a real number.

  • Multiplication of Complex Numbers

    • Note that the FOIL algorithm produces two real terms (from the First and Last multiplications) and two imaginary terms (from the Outer and Inner multiplications).
    • Similarly, a number with an imaginary part of $0$ is easily multiplied as this example shows: $(2+0i)(4-3i)=2(4-3i)=8-6i.$

  • Complex Numbers and the Binomial Theorem

    • In what follows, it is useful to keep in mind the powers of the imaginary unit $i$:
    • If we gather the real terms and the imaginary terms, we have the complex number:

  • Imaginary Numbers

    • There is no such value such that when squared it results in a negative value; we therefore classify roots of negative numbers as "imaginary."
    • That is where imaginary numbers come in.
    • When the radicand (the value under the radical sign) is negative, the root of that value is said to be an imaginary number.
    • Specifically, the imaginary number, $i$, is defined as the square root of -1: thus, $i=\sqrt{-1}$.

  • Addition and Subtraction of Complex Numbers

    • Complex numbers can be added and subtracted by adding the real parts and imaginary parts separately.
    • This is done by adding the corresponding real parts and the corresponding imaginary parts.
    • The key again is to combine the real parts together and the imaginary parts together, this time by subtracting them.
    • we would compute $4-2$ obtaining $2$ for the real part, and calculate $-3-4=-7$ for the imaginary part.
    • Calculate the sums and differences of complex numbers by adding the real parts and the imaginary parts separately

  • Complex Conjugates and Division

    • The real and imaginary parts of a complex number can be extracted using the conjugate, respectively:
    • Neither the real part c nor the imaginary part d of the denominator can be equal to zero for division to be defined.

  • The Discriminant

    • If ${\Delta}$ is positive, the square root in the quadratic formula is positive, and the solutions do not involve imaginary numbers.
    • This means the square root itself is an imaginary number, so the roots of the quadratic function are distinct and not real.

  • Sets of Numbers

    • The set of imaginary numbers, denoted by the symbol $\mathbb{I}$, includes all numbers that result in a negative number when squared.
    • The set of complex numbers, denoted by the symbol $\mathbb{C}$, includes a combination of real and imaginary numbers in the form of $a+bi$ where $a$ and $b$ are real numbers and $i$ is an imaginary number.

  • Defining Trigonometric Functions on the Unit Circle

    • In this section, we will redefine them in terms of the unit circle.
    • Recall that a unit circle is a circle centered at the origin with radius 1.
    • The coordinates of certain points on the unit circle and the the measure of each angle in radians and degrees are shown in the unit circle coordinates diagram.
    • We can find the coordinates of any point on the unit circle.
    • The unit circle demonstrates the periodicity of trigonometric functions.