Help with these two problems in complex analysis

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Homework Help Overview

The discussion revolves around finding the arguments of the complex numbers -4-3i and -4+3i, focusing on the principles of complex analysis related to angle measurement in the complex plane.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the calculation of arguments using arctangent and question the correctness of the original poster's interpretation of their teacher's feedback.

Discussion Status

Some participants affirm the original poster's approach while others suggest that visual aids, such as drawings, might help clarify the understanding of angles in the complex plane. The discussion reflects varying interpretations of angle reference frames.

Contextual Notes

There is mention of the principle of argument and its constraints, including the range of angles considered and the periodic nature of angle measurement in complex analysis.

Mathematicsss

Homework Statement


What is the argument of -4-3i, and -4+3i?

Homework Equations


tantheta=opposite/adjacent side
The principle of argument is that the argument lies between -pi and pi (not including -pi).

The Attempt at a Solution


arg(-4-3i) = -pi + arctan(3/4)
arg(-4+3i) = pi - arctan(3/4)

My teacher wrote on the answer sheet that the argument of -4-3i is just arctan(3/4).. am I incorrect in the above arguments?[/B]
 
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You are correct.
 
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Drawing a picture also will help you figure out an approximate angle, to see if you figured it correctly.
 
Mathematicsss said:

Homework Statement


What is the argument of -4-3i, and -4+3i?

Homework Equations


tantheta=opposite/adjacent side
The principle of argument is that the argument lies between -pi and pi (not including -pi).

The Attempt at a Solution


arg(-4-3i) = -pi + arctan(3/4)
arg(-4+3i) = pi - arctan(3/4)

My teacher wrote on the answer sheet that the argument of -4-3i is just arctan(3/4).. am I incorrect in the above arguments?[/B]
Your prof. may have been referring to the fact that angles in the Complex plane depend on the "frame of reference" for angles, as well as to the periodicity. If , e.g., the x-axis corresponds to 0 , then you will have a certain angle, if you set the y-axis to be the 0 -reference, you will have another angle, etc. This relates to what is called a branch of the associated function of logarithm.
 

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