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Tough Twelve Trig Formulas

  1. Dec 15, 2007 #1
    1. The problem statement, all variables and given/known data

    Prove that: tan (a - b) = tana - tanb
    1 + tanatanb
    ]​

    2. Relevant equations

    cos (a- b) = cosacosb + sinasinb


    sin (a - b) = sinacosb - cosasinb


    3. The attempt at a solution

    I have plugged in the two equations give above since tan - sin/cos and then i'm am stumped of how to proceed

    tan (a - b) = sinacosb - cosasinb
    cosacosb + sinasinb

    can anyone help please?
     
  2. jcsd
  3. Dec 15, 2007 #2

    dynamicsolo

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    Homework Helper

    The formula you are trying to arrive at provides the clue: what could you divide numerator and denominator by to get that "1" in the denominator?
     
  4. Dec 16, 2007 #3
    so times buy a form of one...... 1 over cosacosb?
     
  5. Dec 16, 2007 #4

    rock.freak667

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    Homework Helper

    yes that is correct, divide the numerator and denominator by cosacosb
     
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