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Math Help - prove- trigo

  1. #1
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    Post prove- trigo

    cosA+sinA= sec2A + tan2A
    cosA-sinA

    cotA+tanA=sec2A
    cotA-tanA


    HOW o???
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  2. #2
    Super Member
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    For the first one, multiply by \frac{\cos{A}+\sin{A}}{\cos{A}+\sin{A}}

    You will need the following identities:
    \sin^2{A} + \cos^2{A} = 1

    \cos^2{A} - \sin^2{A} = \cos{2A}

    For number 2, recall that
    \tan{A} = \frac{\sin{A}}{\cos{A}}

    \cot{A} = \frac{\cos{A}}{\sin{A}}

    Replace and combine fractions, then simplify.
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  3. #3
    Junior Member
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    For first one , how about tan2A?
    THX!
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