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Math Help - Confused about complex no

  1. #1
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    Confused about complex no

    Hi can you help me with:

    Suppose z = cis A where A is acute. Find the argument of z + 1:

    I understand how to draw the vectors and all on the Argand diagram, so how the textbook showed it to be is the first picture.


    However,t o find the argument of z+1, I don't understand, my understanding is that the argument of z+1 is the red angle, as shown in the next picture. Why is it wrong? For the answer is that the argument of z+1 is pi/2 since it is a rhombus, but I don't see how, not from my understanding of what a z+1 argument is!

    Please help, thank you so much!
    Thank you!
    Attached Thumbnails Attached Thumbnails Confused about complex no-zic-1.png   Confused about complex no-zic-2.png  
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  2. #2
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    Re: Confused about complex no

    Quote Originally Posted by Tutu View Post
    Suppose z = cis A where A is acute. Find the argument of z + 1: For the answer is that the argument of z+1 is pi/2 since it is a rhombus[/COLOR]

    That is not true.
    You must have misread the question or have left something out.
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  3. #3
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    Re: Confused about complex no

    Confused about complex no-screen-shot-2012-11-29-pm-01.04.35.png

    This is the whole question, complete with solutions. I gathered from here that the argument of z+1 is pi/2. Read it over and still thought so. Maybe my understanding is not good enough..

    Thank you!
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