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Is this a poorly worded question?

  1. Jun 16, 2009 #1
    Example found on a website...(there were no graphs or explanations as to p or r or q)
    Reverse engineering the question from the answer, I found p to be 180.
    --------------------------------------------------------------------------

    A vector that has length 10 makes an angle of p/6 with the x-axis. Find its components.


    Solution:

    x = r cos q, y = r sin q

    So that

    x = (10)(/ 2), y = 10 (1/2) = 5

    We can write the vector as

    5 i + 5j
     
  2. jcsd
  3. Jun 16, 2009 #2
    They are using radian measure, and they meant p = [itex]\pi[/itex] radians which is equivalent to 180 degrees. Radian measure is derived from the unit circle; the radian measure of an angle is given by the length of arc that the angle subtends on a unit circle centered at the vertex of the angle. this makes use of the derived fact that the circumference of a circle is known to be 2[itex]\pi[/itex], so that 360 degrees is 2[itex]\pi[/itex] radians. It is common to leave off the "radian" as a unit of measure since it is also defined as a dimensionless ratio of two lengths (the length of arc divided by the length of the radius of the circle).
     
    Last edited: Jun 16, 2009
  4. Jun 16, 2009 #3
    Thanks
     
  5. Jun 16, 2009 #4
    Is it just me, or does that vector have neither the length nor the angle specified in the original problem?
     
  6. Jun 17, 2009 #5
    yeah. answer is [tex]5\sqrt{3}i + 5j[/tex]

    [tex]\cos (\frac {\pi}{6}) = \frac{\sqrt3}{2}[/tex]
     
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