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Math Help - prove identity help!

  1. #1
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    prove identity help!

    can someone help in prove the identity:

    2sin2 θ
    1+cos2
    is equal to tan2 θ

    in english 2sin sqaured theta divided by 1 + cos2 eqauls to tan squared theta

    any help by great
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  2. #2
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    Do you mean:

    {tan}^2 x = \frac{2{sin}^2 x}{1+cos 2x} ?

    If so, then here's a proof:

    {tan}^2 x = \frac{1 - cos 2x}{1 + cos 2x}

    1 - cos 2x = 1 - (1 - 2{sin}^2 x) = 2{sin}^2 x

    Substitute the new numerator.

    {tan}^2 x = \frac{2{sin}^2 x}{1 + cos 2x}

    QED.
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  3. #3
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    Quote Originally Posted by maths99 View Post
    can someone help in prove the identity:

    \displaystyle\frac{2sin^2\theta}{1+cos2\theta}=tan  ^2\theta


    In english.... 2sin squared theta divided by 1 + cos2theta equals tan squared theta.

    Any help would be great.
    The left-hand-side is expressed in terms of sine and cosine.
    We can also express the right-hand side in terms of sine and cosine...

    \displaystyle\frac{2sin^2\theta}{1+cos2\theta}=\le  ft(\frac{sin\theta}{cos\theta}\right)^2=\frac{sin^  2\theta}{cos^2\theta} ?

    sin^2\theta is common to both sides, so divide both sides by sin^2\theta

    \displaystyle\frac{2}{1+cos2\theta}=\frac{1}{cos^2  \theta} ?

    Divide both sides by 2.

    \displaystyle\frac{1}{1+cos2\theta}=\frac{1}{2cos^  2\theta} ?

    Now you only need determine if the denominators are equal...
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  4. #4
    No one in Particular VonNemo19's Avatar
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    Why do people just go and solve the problem for the newbie? This is his first post and who knows...Maybe this problem is part of a quiz for one of his online assignments....

    Don't be too eager to please guys. That's all I'm saying.

    Peace
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  5. #5
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    thanks for the help
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  6. #6
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    Quote Originally Posted by VonNemo19 View Post
    Why do people just go and solve the problem for the newbie? This is his first post and who knows...Maybe this problem is part of a quiz for one of his online assignments....

    Don't be too eager to please guys. That's all I'm saying.

    Peace
    To whom?
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  7. #7
    No one in Particular VonNemo19's Avatar
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    Quote Originally Posted by Archie Meade View Post
    To whom?
    Archie Meade. I've watched you for a while and you are genuinely here as a helper. Your reply worked as a guide for the newb. So, rest assured, that I wasn't directing my post to you. Let's have a logic session, shall we?

    \text{ArchieMeade}\wedge\text{elemental}

    \neg\text{ArchieMeade}

    \rightarrow{elemental}
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  8. #8
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    just to let you know it wasnt part of an assignment or on line test. just im doing lots to gain practise in my civil engineer course, and was stuck on this. thanks for your help peace
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