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Posted by on Tuesday, June 7, 2011 at 4:26pm.

I get that we have to put it into radical form, but I don't understand the process. Can someone walk me through it and explain it?

arccos(-1/2)

  • trig - , Tuesday, June 7, 2011 at 5:12pm

    you want the angle Ø so that
    cosØ= -1/2
    We know that if the cosØ is negative, then Ø is in either the II or III quadrant
    we also know that cos 60° =+1/2

    so Ø = 180-60 or 180+60
    Ø = 120° or 240°
    in radians it would be 2π/3 or 4π/3

    your calculator will only give you the angle closest to the origin,

    inter

    2nd
    cos
    -.5
    =

    and you will get 120 if your calculator is set to degrees.

  • trigononometry - , Friday, June 17, 2011 at 7:52am

    (12x2.17)
    cos0 120.6

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