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Math Help - how can i geta fraction to radians

  1. #1
    Newbie
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    Sep 2005
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    how can i geta fraction to radians

    how do i get
    this into radians
    sin(x) = 5/13
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  2. #2
    MHF Contributor
    Joined
    Apr 2005
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    sin(x) = 5/13

    That implies you want to find angle x, not the 5/13, in radians.

    5/13 is just a number here. It is the value of the sine of angle x.
    If you said "find 5/13 in radians", without showing the sin(x), them 5/13 is already in radians. Or get it in decimals, 5/13 = 0.384615385. So, 5/13 = 0.384615385 radians.

    Back to your equation,
    sin(x) = 5/13
    That is a positive sine value. Sine is positive in the 1st and 2nd quadrants, so, you'd get two answers for x if x is from 0 to 2pi radians only.

    sin(x) = 5/13
    sin(x) = 0.384615385
    Take the arcsines of both sides,
    arcsin[sin(x)] = arcsin(0.384615385)
    x = arcsin(0.384615385)
    Using a calculator,
    x = 0.39479112 radians ---in the 1st quadrant.
    x = pi -0.39479112 = 2.74680153 radians ----in the 2nd quadrant.
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