Complex Analysis: Express f(z)= (z+i)/(z^2+1) as w=u(x,y)+iv(x,y)

In summary, the conversation is about trying to write the function f(z)=(z+i)/(z^2+1) in the form w=u(x,y)+iv(x,y). The person is struggling to get the correct answer and is asking for a hint. They eventually figure out that they need to rewrite the denominator as (z+i)(z-i) in order to do the partial fraction.
  • #1
physicsnewb7
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Homework Statement


write f(z)= (z+i)/(z^2+1) in the form w=u(x,y)+iv(x,y)


Homework Equations





The Attempt at a Solution


I tried using the conjugate and also expanding out algebraically but I can not seem to get the right answer. I know what the answer is, x/(x^2+(y-1)^2)+i(1-y)/(x^2+(y-1)^2) but I fail to see how to get there. am I doing something wrong?
 
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  • #2
all i want is a simple hint i don't want anyone to do the problem for me I just want a little help. just a little push in the right direction would be so helpful.
 
  • #3
Why don't you try and do the partial fraction. I think it should work.
 
  • #4
rizardon said:
Why don't you try and do the partial fraction. I think it should work.

So I do the partial fraction after i expand out? expanding (z+i)/(z^2+1) I get (x+yi+i)/(x^2+2xyi-y^2+1) how am I supposed to factor the denominator?
 
  • #5
ohhhhh nevermind i finally got it you rewrite the denominator as (z+i)(z-i) then do the partial fraction. so simple! you were right rizardonthanks
 

1. What is complex analysis?

Complex analysis is a branch of mathematics that studies functions of complex variables. It deals with the properties and behavior of functions that have complex inputs and outputs, and how these functions can be manipulated and analyzed.

2. What is the function f(z) = (z+i)/(z^2+1)?

This function is a rational function that takes a complex number z as an input and outputs another complex number. It is a specific example of a rational function, which is a function that can be written as the ratio of two polynomial functions. In this case, the numerator is z+i and the denominator is z^2+1.

3. How do you express a complex function in terms of real and imaginary parts?

To express a function in terms of real and imaginary parts, we use the Euler's formula, e^(ix) = cos(x) + i*sin(x). By substituting e^(ix) for z in the function f(z), we can rewrite it as w = (e^(ix)+i)/(e^(2ix)+1). Then, we can expand the numerator and denominator using the binomial theorem and simplify to get the real and imaginary parts of w in terms of x and y.

4. How do you find the real and imaginary parts of the function f(z) = (z+i)/(z^2+1)?

To find the real and imaginary parts of this function, we can use the method mentioned in the previous question. After expanding and simplifying, we get u(x,y) = (x-y)/(x^2+y^2+1) and v(x,y) = (x+y)/(x^2+y^2+1). These are the real and imaginary parts of the function w = u(x,y)+iv(x,y).

5. How do you plot the function f(z) = (z+i)/(z^2+1)?

To plot this function, we can use the real and imaginary parts we found in the previous question. We can plot points on the complex plane using the values of x and y, and connect them to create a graph. This graph will show the behavior of the function as it takes different complex values as inputs.

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