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Complex Numbers

The square root of negative one, which we now call the imaginary unit, was once thought to be an absurd notion. However, through the diligent studies of open-minded mathematicians, it was shown that the real numbers were actually just one part of a larger set of numbers known as the complex numbers, the other part being the imaginary numbers. Please direct all questions about these surprisingly useful and applicable numbers into this category.

887 Questions

Why is reactance imaginary?

The reactance is taken imaginary because it does not consume any power directly but reactance like inductive or capacitive reactance provides phase shift of 90 degree, whether it provides a leading phase shift or lagging phase shift. In case of inductor the current lags voltage by 90 degree while in case of capacitor current leads by 90 degree. Thus only resistance is taken as real while combination of resistance and capacitance is called impedence....

Ashish Sharma AP ECE

HIET Shahpur

How do you express a number in scientific notation's and scientific notation's to decimal notation's?

Assuming x is your number, x * 10^n = x moved n decimal places.

When n is positive, move the decimal point n places to the right.

When n is negative, move the decimal point n places to the left.

When n is 0, do nothing.

What is complex solution?

a more detailed solution of an answer

What does 360 million written in number terms look like?

It is: 360,000,000 or as 3.6*108 in scientific notation

What are pure imaginary numbers?

complex numbers with no real part
if any complex number z can be written a + i b
then pure imaginary numbers have a=0 and b not equal to 0

Is the square root of -24 rational?

No. The square root of -24 isn't even real, let alone rational because the square root of any negative number is going to be an imaginary number.

What number is the additive identity in the set of real numbers?

Zero is the additive identity in the set of real numbers; when you add zero to any number, the number does not change its identity.

How do you simplify 4i 3i?

Assume we have the product of these terms. Multiply these terms altogether to get 12i². Make note that i = √-1, i² = -1, i³ = -i and i⁴ = 1. Then, 12i² = 12(-1) = -12.

That is the answer to the question.

What is self conjugate of complex number?

Aamir jamal;

All real numbers are complex numbers with 0 as its imaginary part.A real number is

self-conjugate.

e.g;a+0i

self conjugate =a-0i i=iota

How do you plot 6-i on a complex plane?

You go 6 in positive x-direction ("right") and one in negative y-direction ("down"), there is your complex number, drwa an arrow reaching from the center to this point.

When were complex numbers developed?

The concept of a complex number appears to be first conceived by Gerolamo Cardano (about 1545). See Related Link. The work of Euler in the 1700's helped to make them more useful, though.

What is a non-real complex?

A complex number x+iy is non-real if x=0 like 0+i13

Why are the absolute values of a complex number and its conjugate always equal?

If you understand what the absolute value of a complex number is, skip to the tl;dr part at the bottom.

The absolute value can be thought of as a sorts of 'norm', because it assigns a positive value to a number, which represents that number's "distance" from zero (except for the number zero, which has an absolute value of zero).

For real numbers, the "distance" from zero is merely the number without it's sign.

For complex numbers, the "distance" from zero is the length of the line drawn from 0 to the number plotted on the complex plane.

In order to see why, take any complex number of the form a + b*i, where 'a' and 'b' are real numbers and 'i' is the imaginary unit. In order to plot this number on a complex plane, just simply draw a normal graph. The number is located at (a,b).

In order to determine the distance from 0 (0,0) to our number (a,b) we draw a triangle using these three points:

(0,0)

(a,0)

(a,b)

Where the points (0,0) and (a,b) form the hypotenuse. The length of the hypotenuse is also the "distance" of a + b*i from zero. Because the legs run parallel to the x and y axes, the lengths of the two legs are 'a' and 'b'.

By using the Pythagorean theorem, we can find the length of the hypotenuse as (a2 + b2)(1/2).

Because the length of the hypotenuse is also the 'distance' of the complex number from zero on the complex plane, we have the definition:

|a + b*i| = (a2 + b2)(1/2)

ALRIGHT, almost there.

tl;dr:

Remember that the complex conjugate of a complex number a + b*i is a + (-b)*i. By plugging this into the Pythagorean theorem, we have:

b2 = (-b)2

So:

(a2 + (-b)2)(1/2) = (a2 + b2)(1/2)

QED.

What is the name of 3.1415926535?

That's an approximation of "pi", truncated after ten decimal places.

Why was complex numbers discovered?

They were discovered when Cardano solved the third degree equation.

In the formulas that arose to solve the third degree equation, Cardano needed to take the square root of negative numbers and add them up in a certain way. The strange thing that happened was that the formulas used these complex numbers, even if the solutions to the equation where all real. This baffled the mathematicians of the time, because how could these strange numbers turn out to be "real"?

Later this was considered totally correct, when the field of complex numbers was better undestood.

How many rotation symmetry does a diamond have?

A diamond has two rotation symmetry. It is possible to have a diamond that does have four of rotation symmetry.