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Math Help - proving for tan question

  1. #1
    Junior Member
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    proving for tan question

    Hey need some help with this one

    Prove that tan (\theta +\phi ) = (tan \theta + tan \phi) \div ( 1 - tan \theta . tan \phi )

    Cheers
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  2. #2
    MHF Contributor Amer's Avatar
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    \sin ( \theta + \phi ) = \sin \theta \cos \phi + \cos \theta \sin \phi

    \cos (\theta + \phi ) = \cos \theta \cos \phi - \sin \theta \sin \phi

    \tan (\theta + \phi ) = \frac{\sin \theta \cos \phi + \cos \theta \sin \phi }{\cos \theta \cos \phi - \sin \theta \sin \phi}

    divide the denominator and nominator by \cos \phi \cos \theta

    you will get the identity
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  3. #3
    Junior Member
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    Thumbs up

    thanks for the reply Amer

    got the answer out now
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