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anonymous

  • one year ago

Can someone please help me finish this pre-calc question??? Express the complex number in trigonometric form. 2 - 2i This is what I have so far: r=absolute value(2-2i) r= sqrt((2)^2+(-2)^2) r=sqrt(8) r=2sqrt(2) theta(ref)=tan^-1*absolute value(2/-2) theta(ref)=pi/2 I dont know how to get the value of theta alone to complete this problem. What do i do next? Please help!

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  1. anonymous
    • one year ago
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    \[2-2i\]\[r=\sqrt{2^2+(-2)^2}\]\[\tan^{-1} = (\frac{ -2 }{ 2 } ) = ?\]

  2. anonymous
    • one year ago
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    you arent suppose to use radian mode for polar form

  3. anonymous
    • one year ago
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    thats why you got pi/2

  4. anonymous
    • one year ago
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    I thought \[\tan^{-1} =\frac{ a }{ b }\]

  5. anonymous
    • one year ago
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    no its b/a

  6. anonymous
    • one year ago
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    |dw:1439092982007:dw|

  7. anonymous
    • one year ago
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    better if i draw it out?

  8. anonymous
    • one year ago
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    Yes. After switching it to b/a i got theta(ref)=-1

  9. anonymous
    • one year ago
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    find out whats tan^1(-1)

  10. anonymous
    • one year ago
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    tan^1(-1) or tan^-1(1)? tan^1(-1) is -1.55 or -tan(1) http://www.wolframalpha.com/input/?i=tan%5E1%28-1%29

  11. anonymous
    • one year ago
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    \[\tan^{-1} (-1)\]

  12. anonymous
    • one year ago
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    Okay, yeah tan^-1(-1) is -pi/4 or -45 degrees

  13. anonymous
    • one year ago
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    now put that in 360 degrees form

  14. anonymous
    • one year ago
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    find the angle that is coterminal to -45 degrees? Thats 315, right?

  15. anonymous
    • one year ago
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    yea

  16. anonymous
    • one year ago
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    you know how to make the polar form from there right?

  17. anonymous
    • one year ago
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    oh wait its trigo form

  18. anonymous
    • one year ago
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    Yea. I was stuck at theta(ref)= -1. I dont know what to do next

  19. anonymous
    • one year ago
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    ok great you have the angles now you can form whatever it is

  20. anonymous
    • one year ago
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    you should get \(\theta\) instantly from your eyeballs

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