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Math Help - [SOLVED] Is this statement true?

  1. #1
    Junior Member moonman's Avatar
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    [SOLVED] Is this statement true?

    cos(A + B) / sinA cosB = cotA - tanB
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  2. #2
    Moo
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    Hello,
    Quote Originally Posted by moonman View Post
    cos(A + B) / sinA cosB = cotA - tanB
    cos(A+B)=cos(A)cos(B)-sin(A)sin(B)

    So cos(A+B)/sinA cosB=cos(A)/sin(A) - sin(B)/cos(B)
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  3. #3
    Junior Member moonman's Avatar
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    Quote Originally Posted by Moo View Post
    Hello,

    cos(A+B)=cos(A)cos(B)-sin(A)sin(B)

    So cos(A+B)/sinA cosB=cos(A)/sin(A) - sin(B)/cos(B)
    Awesome
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  4. #4
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    Quote Originally Posted by moonman View Post
    cos(A + B) / sinA cosB = cotA - tanB
    hey mate,

    cos(A+B) = cos(A)cos(B) - sin(A)sin(B)

    Thus,

    cos(A+B)/(sin(A)cos(B)) = ( cos(A)cos(B) - sin(A)sin(B) )/ (sin(A) cos(B))
    = (cos(A)cos(B))/(sin(A)cos(B)) - (sin(A)sin(B))/(sin(A)cos(B) )
    = (cos(A)/sin(A)) - (sin(B)/cos(B))
    = cot(A) - tan(B)

    So yes its true!

    Hope this helps,

    David
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