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dumbsearch2

  • one year ago

Write z = -5 + 5i in trigonometric form.

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  1. dumbsearch2
    • one year ago
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  2. dumbsearch2
    • one year ago
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    D?

  3. anonymous
    • one year ago
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    |dw:1441163170659:dw|

  4. surry99
    • one year ago
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    Hint:Sketch the point it on the complex plane

  5. dumbsearch2
    • one year ago
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    I found -(pi)/(4)

  6. dumbsearch2
    • one year ago
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    before

  7. anonymous
    • one year ago
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    ??

  8. anonymous
    • one year ago
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    |dw:1441163275849:dw|

  9. dumbsearch2
    • one year ago
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    What does that graph mean?

  10. jim_thompson5910
    • one year ago
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    -5 + 5i is in the form a+bi a = -5 b = 5 you can plot a+bi on the complex number plane as the ordered pair (a,b) which is why satellite73 plotted the point (-5,5)

  11. anonymous
    • one year ago
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    it means the angle is easy to find if you use arctangent here it will not work because you are in the wrong quadrant

  12. jim_thompson5910
    • one year ago
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    http://img.sparknotes.com/figures/A/a28868a2f5deab01f6e8c7727c2ee7a4/complexplane.gif

  13. anonymous
    • one year ago
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    if you took \(\tan^{-1}(-1)\) you get \(-\frac{\pi}{4}\) but you are not in quadrant 4, you are in quadrant 2

  14. dumbsearch2
    • one year ago
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    So it's 3pi/4 instead, right?

  15. anonymous
    • one year ago
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    yes

  16. anonymous
    • one year ago
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    you cannot use arctan unless you are in quadrant 1 or 4

  17. jim_thompson5910
    • one year ago
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    well you can use arctan, just add on pi to get to the right quadrant

  18. dumbsearch2
    • one year ago
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    ?

  19. anonymous
    • one year ago
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    you have to either know it, or use \[\cos(\theta)=\frac{a}{r}\] and \[\sin(\theta)=\frac{b}{r}\]

  20. jim_thompson5910
    • one year ago
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    as satellite73 said, arctan(-1) = -pi/4 add on pi to get to 3pi/4 (-pi/4) + (pi) = (-pi/4) + (4pi/4) = (-pi+4pi)/4 = 3pi/4

  21. anonymous
    • one year ago
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    or what @jim_thompson5910 said, but in any case you have to know what quadrant you are in before you start

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