Working complex fractions without conjugate method

In summary, the conversation discusses a question that requires an answer in polar form without using the complex conjugate method. The person is unsure of the correct method to use and is considering converting to polar form or using normal addition/subtraction of fractions. They also question if using (a-bi)/(a^2+b^2) is considered using the complex conjugate method.
  • #1
LF07LAN
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Homework Statement


Ive been given a question that requires an answer in polar form but the method I must use is the normal addition/subtraction of fractions. This throws me because I'm sure there is a simple method for the reciprocal of a complex number.

Q. 1/(13- 5i) - 1/(2-3i)

Homework Equations



where z = a + bi
i'm aware of how to change to polar for whole numbers and how to get where I want using the conjugate method but can't fathom the correct start point.


The Attempt at a Solution



I considered 1/13 - 1/5i using the rules of fractions but wasn't convinced.
The alternative was to convert straight to polar using 1 / 0degrees over the (13-5i in polar form)
 
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  • #2
[tex]\frac{1}{a+ bi}= \frac{1}{a+ bi}\frac{a- bi}{a- bi}= \frac{a- bi}{(a+ bi)(a- bi)}[/tex]
[tex]= \frac{a- bi}{a^2-b^2i^2}= \frac{a- bi}{a^2+ b^2}[/tex]

(Even for real numbers,
[tex]\frac{1}{a+ b}\ne \frac{1}{a}+ \frac{1}{b}[/tex])
 
  • #3
Doesn't that just proove the Complex Conjugate method? I can only solve the answer without the use of this method.

The actual wording of the question is:
Evaluate the following expression using normal addition/subtraction of fractions and/or polar form (i.e DO NOT use the complex conjugate method) giving the result in polar form.

if I use (a-bi)/(a2 + b2) doesn't this just mean I've used the complex Conjugate Method? Or ar you saying I can do it this way:

where a^2 + b^2 = 13^2 + 5^2 = 194

13/194 + (5/194)i

0.067 + 0.026i
and the same for the second rectangular element of the question (1/(2-3i)
 
  • #4
Welcome to PF.

I think "normal addition/subtraction of fractions" means you find a common denominator for the two fractions, and then you can add the resulting numerators.
 

1. How do I simplify complex fractions without using the conjugate method?

One approach to simplifying complex fractions without using the conjugate method is to first convert the complex fractions into simpler fractions by finding a common denominator. Then, simplify the numerator and denominator separately before dividing the simplified numerator by the simplified denominator.

2. Can complex fractions be simplified without using the conjugate method?

Yes, complex fractions can be simplified without using the conjugate method. However, this method may be more time-consuming and may require a good understanding of fraction operations.

3. What is the advantage of using the conjugate method when working with complex fractions?

The conjugate method is a quick and effective way to simplify complex fractions. It involves multiplying the numerator and denominator by the conjugate of the denominator, which eliminates the complex numbers and leaves a simplified fraction. This method is especially useful when working with algebraic expressions.

4. Are there any situations where the conjugate method is not applicable?

The conjugate method may not be applicable if the complex fraction does not have a conjugate or if the conjugate still contains complex numbers. In such cases, other methods such as finding a common denominator may be more suitable.

5. Can the conjugate method be used for both addition and subtraction of complex fractions?

Yes, the conjugate method can be used for both addition and subtraction of complex fractions. The only difference is in the sign of the conjugate used in the multiplication step. For addition, the conjugate should have the same sign as the denominator, while for subtraction, the conjugate should have the opposite sign.

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