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    Find in ssurd fortm, the exacty value of cos 75 - whats the easiest way to do it?
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    (Original post by TheWolf)
    Find in ssurd fortm, the exacty value of cos 75 - whats the easiest way to do it?
    i would do cos 75 = cos(30+45),
    now use the identity cos(A+B) = cosAcosB - sinAsinB
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    (Original post by TheWolf)
    Find in ssurd fortm, the exacty value of cos 75 - whats the easiest way to do it?
    Cos(45 + 30) = Cos45Cos30 - Sin45Sin30.

    You should know the values of these as they're all standard forms.
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    (Original post by TheWolf)
    Find in ssurd fortm, the exacty value of cos 75 - whats the easiest way to do it?
    If you use the cos(A+B) rule and split up the 75 into terms that you can workout.

    So cos75 = cos(30 + 45)

    = cos30cos45 - sin30sin45

    cos 30 = (sqrt3)/2
    sin 45 = cos 45 = 1/(sqrt 2)
    sin 30 = 1/2

    sub all these values into the equation and voila!!! There's you ans in surd form

    Hope that makes sense

    Edit: Mockel and Mysticmin beat me to it!!!
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    Damn, mockel beat me to it
 
 
 
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Updated: June 19, 2004
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