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Math Help - Finding the value of sin x

  1. #1
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    Finding the value

    Ah, my title ! I'm sorry !
    I was looking at the wrong question. Heh.

    If f (x/x+1) = 1/x,
    x cannot be = 0, 1, and
    0 <= theta <= pi/2,
    then simplify
    f (1/cos^2theta)

    Thanks in advance : D
    Last edited by ahling; July 28th 2008 at 03:48 PM.
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by ahling View Post
    Ah, my title ! I'm sorry !
    I was looking at the wrong question. Heh.

    If f (x/x+1) = 1/x,
    x cannot be = 0, 1, and
    0 <= theta <= pi/2,
    then simplify
    f (1/cos^2theta)

    Thanks in advance : D
    For a non exeptional x , let:

    y=\frac{x}{x+1}

    so:

    x=\frac{-y}{y-1}

    so (for non-exceptional \theta ):

    f(1/\cos^2(\theta))=\frac{1-[1/\cos^2(\theta)]}{[1/\cos^2(\theta)]}

    Now simplify.

    RonL
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  3. #3
    Senior Member nikhil's Avatar
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    Quote Originally Posted by ahling View Post
    Ah, my title ! I'm sorry !
    I was looking at the wrong question. Heh.

    If f (x/x+1) = 1/x,
    x cannot be = 0, 1, and
    0 <= theta <= pi/2,
    then simplify
    f (1/cos^2theta)

    Thanks in advance : D
    f (x/x+1) = 1/x
    Now in place of x put 1/x
    f (1/x+1) = x
    f (1/cos^2theta)=f (1/1-sin^2theta)=-sin^2theta
    where sintheta cannot be = 0, 1,
    Last edited by nikhil; July 29th 2008 at 03:43 AM.
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  4. #4
    Grand Panjandrum
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    Quote Originally Posted by nikhil View Post
    f (x/x+1) = 1/x
    Now in place of x put 1/x
    f (1/x+1) = x
    f (1/cos^2theta)=f (1/1-sin^2theta)=-sin^2theta
    where sintheta cannot be = 0, 1,
    Like I should have told the OP use brackets to remove the ambiguity of expressions like 1/x+1 or x/x+1.

    RonL
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