Finding the Center and Radius of a Circle with Complex Numbers and Loci

In summary, the conversation discusses finding the centre point and radius of a circle given a specific argument. The method used involves expressing the ratio of the complex numbers in terms of real and imaginary parts and using the equation for a circle to solve for the radius. The resulting radius is 5 unit^2.
  • #1
Kajan thana
151
18

Homework Statement



Sketch the loci, find centre point and the radius of the circle.
args((z-3i)/((z+4))=π/6[/B]

Homework Equations


args(x/y)=args(x)-args(y)
Circle theorem - inclined angle theorem

The Attempt at a Solution



I sketched the circle with major arc.
Radius= using Pythagorus I got the radius as 5 unit^2 .
H=O/sinθ . H=2.5/sin(π/6)

I am stuck on finding the centre point.

[/B]
 
Physics news on Phys.org
  • #2
Can you find one or two points on the circle?
 
  • #3
Kajan thana said:

Homework Statement



Sketch the loci, find centre point and the radius of the circle.
args((z-3i)/((z+4))=π/6[/B]

Homework Equations


args(x/y)=args(x)-args(y)
Circle theorem - inclined angle theorem

The Attempt at a Solution



I sketched the circle with major arc.
Radius= using Pythagorus I got the radius as 5 unit^2 .
H=O/sinθ . H=2.5/sin(π/6)

I am stuck on finding the centre point.
[/B]

Your radius is wrong.

Write ##z = x + iy## and express the ratio ##(z-3i)/(z+4)## as ##A(x,y) + i B(x,y)##. How can you get the equation of the curve in terms of the functions ##A(x,y)## and ##B(x,y)##?
 
  • #4
Ray Vickson said:
Your radius is wrong.

Write ##z = x + iy## and express the ratio ##(z-3i)/(z+4)## as ##A(x,y) + i B(x,y)##. How can you get the equation of the curve in terms of the functions ##A(x,y)## and ##B(x,y)##?
I don't know how to change it into that form.
 
Last edited:
  • #5
mfb said:
Can you find one or two points on the circle?
The coordinates are (0,3) and (-4,0)
 
  • #6
Kajan thana said:
I don't know how to change it into that form.
With a complex z and c:$$\frac c z = \frac{cz^*}{zz^*}$$
Here * is the complex conjugation. Now the denominator is real and you can split the fraction into real and imaginary part.
 
  • #7
mfb said:
With a complex z and c:$$\frac c z = \frac{cz^*}{zz^*}$$
Here * is the complex conjugation. Now the denominator is real and you can split the fraction into real and imaginary part.
I finally got the answer right and the radius is 5 unit^2. Your way gave me the same answer as well.
Thank you so much.
 

1. What are complex numbers and why are they important in mathematics?

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 (i.e. the square root of -1). They are important in mathematics because they allow us to solve equations that cannot be solved with real numbers alone, and they have many practical applications in fields such as engineering and physics.

2. How do you graph complex numbers on the complex plane?

To graph a complex number on the complex plane, plot the real part of the complex number on the x-axis and the imaginary part on the y-axis. The point where these two values intersect is the location of the complex number on the complex plane.

3. What is a locus and how is it related to complex numbers?

A locus is the set of all points that satisfy a given condition or equation. In the context of complex numbers, a locus can be represented as a geometric shape on the complex plane. For example, the locus of points with a fixed distance from a given complex number is a circle on the complex plane.

4. How do you find the equation of an arc on the complex plane?

To find the equation of an arc on the complex plane, you first need to determine the center point and radius of the arc. Then, you can use the equation (x-c)^2 + (y-d)^2 = r^2, where (c,d) is the center point and r is the radius, to represent the arc on the complex plane.

5. What is the principal branch of a complex logarithm?

The principal branch of a complex logarithm is the branch that gives the "principal" or main value of the logarithm. It is defined as the logarithm of a complex number that has a positive real part and an argument in the interval (-π,π]. This branch is often used in calculations involving complex numbers.

Similar threads

  • Precalculus Mathematics Homework Help
Replies
7
Views
2K
  • Precalculus Mathematics Homework Help
Replies
4
Views
3K
  • Precalculus Mathematics Homework Help
Replies
12
Views
1K
  • Precalculus Mathematics Homework Help
Replies
5
Views
2K
  • Precalculus Mathematics Homework Help
Replies
18
Views
2K
  • Precalculus Mathematics Homework Help
Replies
3
Views
1K
  • Precalculus Mathematics Homework Help
2
Replies
52
Views
2K
  • Precalculus Mathematics Homework Help
Replies
1
Views
1K
  • Linear and Abstract Algebra
Replies
1
Views
925
  • Precalculus Mathematics Homework Help
2
Replies
39
Views
4K
Back
Top