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Math Help - Converting to polar (easy)

  1. #1
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    Converting to polar (easy)

    I'm converting -3,4 to polar.

    I have come up with r = +/ 5

    And tan (x) = -4/3

    When I do x = arctan (-4/3)
    in my calculator I get -.927 but the book has 2.214

    Why?

    Thanks.
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  2. #2
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    Re: Converting to polar (easy)

    Quote Originally Posted by minneola24 View Post
    I'm converting -3,4 to polar.
    Let \theta  = \pi  + \arctan \left( {\frac{{ - 4}}{3}} \right)

    Then the polar form of (-3,4) is (5\cos(\theta),5\sin(\theta))~.
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    Re: Converting to polar (easy)

    I'm confused why your adding pie,

    And the book has 5,2.21. And -5, 5.356. As answers
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    Re: Converting to polar (easy)

    Quote Originally Posted by minneola24 View Post
    I'm confused why your adding pie,
    And the book has 5,2.21. And -5, 5.356. As answers
    Have a look at this webpage. You will see the reply is correct.

    The point (-3,5)\in II and {\frac{-\pi}{2}<\arctan \left( {\frac{{ - 4}}{3}} \right)}<0 therefore adding \pi gives the correct second quadrant angle.
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