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Math Help - degree radius-vectors

  1. #1
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    degree radius-vectors

    Calculate the angles degree between the radius-vector of the point and the positive x-axis (measured counter-clockwise from the positive x-axis, within the limits of 180 degrees to positive 180 degrees)
    ^? what do i do? and how do i approach this problem?


    x=-3.93
    y=-3.18
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  2. #2
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    Are you saying your teacher gave you this, but did not cover it during classes?
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  3. #3
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    yea you could say that
    i've never seen this before and i'm in pre-calculus!!
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  4. #4
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    Quote Originally Posted by gabriel View Post
    Calculate the angles degree between the radius-vector of the point and the positive x-axis (measured counter-clockwise from the positive x-axis, within the limits of 180 degrees to positive 180 degrees)
    ^? what do i do? and how do i approach this problem?


    x=-3.93
    y=-3.18
    1. Draw a sketch.

    2. Use the indicated right triangle to determine "the" angle. I didn't understand which angle was meant: The yellow one or the blue one?
    Attached Thumbnails Attached Thumbnails degree radius-vectors-winklvektor.png  
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  5. #5
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    For this you would use the Tangent rule.

    \mbox{angle} = tan^{-1}\left(\dfrac{\mbox{opposite length}}{\mbox{adjacent length}}\right)

    Substitute in the lengths, solve the angle to find the angle between the line and the closest x-axis. Then add the extra angles to find your total angle from the positive x-axis going counter-clockwise.
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  6. #6
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    Well, keep it simple: just get angle opposite the side length 3.18, add 180.
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