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Thread: cotangent

  1. October 2nd 2008, 01:48 AM #1
    maeca
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    cotangent

    Can I distribute cotangent here???

    cot(Arccot 3 + Arccot 7 + Arccot 15 + Arccot 21)

    Can you please show the solution???
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  2. October 2nd 2008, 03:29 AM #2
    bobak
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    Quote Originally Posted by maeca View Post
    Can I distribute cotangent here???

    cot(Arccot 3 + Arccot 7 + Arccot 15 + Arccot 21)

    Can you please show the solution???
    nope you cannot distribute the cotangent here, you will need to use the double angle formula here (several times)

    first note that \cot ( A + B ) = \frac{\cot A \cot B - 1}{\cot A + \cot B}

    so your thing becomes

    \cot( accot 3 + acot 7 + acot 15 + acot 21) = \frac{\cot (accot 3 + acot 7) \cot (acot 15 + acot 21) - 1}{\cot (accot 3 + acot 7) + \cot (acot 15 + acot 21)}<br />

    can you finish this off ?

    Bobak
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