- #1
Calpalned said:|z−1|=2=x2+y2−1−−−−−−−−−√|z-1|=2=\sqrt{x^2+y^2-1}
Expressing z into its real and imaginary parts:Calpalned said:Homework Statement
View attachment 90170
I don't understand example 2. For part a, I got a slightly different answer.
Homework Equations
see picture
The Attempt at a Solution
##|z-1|=2=\sqrt{x^2+y^2-1}##
##4=x^2+y^2-1 \neq (x-1)^2+y^2##
Given ##|z-1|## how did you decide to make the substitution of ##u=x-1##? Why not ##y-1##? So my method was incorrect? While it is true that ##|z| = \sqrt{x^2 +y^2}##, ##|z-1| \neq \sqrt{x^2 +y^2-1}##? Thank you.SteamKing said:Expressing z into its real and imaginary parts:
z = x + iy
We can also create another complex number, w, such that:
w = u + iv
We can also specify that
u = x - 1
v = y
So that
w = u + iv = (x-1) + iy = z - 1
If we let the modulus of (z - 1) = 2, then
|w| = |z - 1| = 2
then by the definition of the modulus of a complex number, we get
|w| = (u2 + v2)1/2 = 2
Squaring both sides and substituting for u and v,
u2 + v2 = 4 or
(x - 1)2 + y2 = 4
which is the equation of a circle of radius = 2 centered at (1, 0).
Ok, this method makes a lot of sense. But just to clarify, was it wrong that I approached this question with ##|z-1|=\sqrt{x^2+y^2-1}##Mark44 said:Geometrically, the equation |z - 1| = 2 represents all of the points z in the complex plane that are 2 units away from 1; i.e., 1 + 0i. The geometry here should suggest that we're dealing with a circle of radius 2, centered at (1, 0).
For the algebra, a slightly different tack from the one SteamKing took...
##|z - 1| = 2##
##\Rightarrow |x + yi - 1| = 2##
##\Rightarrow \sqrt{ [(x - 1) + yi] \cdot [(x - 1) - yi]} = 2## (using the fact that ##|z| = \sqrt{z \cdot \bar{z}}##)
##\Rightarrow \sqrt{(x - 1)^2 + y^2} = 2##
##\Rightarrow (x - 1)^2 + y^2 = 4##
Yes, because ##\sqrt{x^2+y^2-1} \ne \sqrt{(x - 1)^2 + y^2}##Calpalned said:Ok, this method makes a lot of sense. But just to clarify, was it wrong that I approached this question with ##|z-1|=\sqrt{x^2+y^2-1}##
Okay thank youMark44 said:Yes, because ##\sqrt{x^2+y^2-1} \ne \sqrt{(x - 1)^2 + y^2}##
It is easier for me to follow Mark44's method, but I still thank you for your response.Calpalned said:Given ##|z-1|## how did you decide to make the substitution of ##u=x-1##? Why not ##y-1##? So my method was incorrect? While it is true that ##|z| = \sqrt{x^2 +y^2}##, ##|z-1| \neq \sqrt{x^2 +y^2-1}##? Thank you.
Not even close. Subtracting 1 from z doesn't translate into subtracting 1 from the stuff inside the radical. The operations involved are very non-linear.Calpalned said:So my method was incorrect? While it is true that ##|z| = \sqrt{x^2 +y^2}##, ##|z-1| \neq \sqrt{x^2 +y^2-1}##?
Complex numbers are numbers that can be expressed in the form a + bi, where a and b are real numbers and i is the imaginary unit (√-1). Real numbers only have one part, while complex numbers have both a real and imaginary part. This means that complex numbers can represent both real and imaginary quantities, while real numbers can only represent real quantities.
Complex numbers can be represented and manipulated using the Cartesian coordinate system, where the real part is plotted on the x-axis and the imaginary part is plotted on the y-axis. They can also be represented using polar coordinates, where the magnitude and angle are used to describe the complex number. Complex numbers can be added, subtracted, multiplied, and divided using specific rules, just like real numbers.
Complex numbers have many applications in mathematics, physics, and engineering. They are used to solve equations that involve imaginary solutions, such as in electrical circuits and signal processing. They are also used in fields such as quantum mechanics, fluid dynamics, and computer graphics.
Yes, complex numbers can have a negative real part or imaginary part. The real part can be negative if the number is located in the third or fourth quadrant of the complex plane, while the imaginary part can be negative if the number is located in the second or third quadrant.
Complex numbers are closely related to trigonometric functions. They can be expressed using Euler's formula: e^(ix) = cos(x) + i sin(x). This means that the trigonometric functions cosine and sine can be represented using complex numbers. This relationship is useful in solving equations involving trigonometric functions and in understanding the behavior of periodic functions.