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-cos(60) = cos(60)?

  1. May 12, 2005 #1
    I was thinking about this, and wanted to know if it was true...

    -cos(60) = cos(-60) = cos(300) = cos(60)
  2. jcsd
  3. May 12, 2005 #2


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    no its not,

    cos(-x) = cos(x) ( cos is an even function )

    If you draw these angles over the unit circle, then cos(x) refers to the x component of where the ray intersects the circle. For 60 degrees and -60 degrees, the x component lies to the right of the y axis, so both are positive (and equal).
  4. May 12, 2005 #3
    Ok, thanks for clearing that up for me.
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