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Math Help - Help with Compound Angle Formulae

  1. #1
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    Help with Compound Angle Formulae

    Hi guys! How do you solve this question?

    1. Tan 75 (using the compound angle formulae)

    8. a) Develop formulas for cot(α + β) and cot(α - β).
    b) Find cot 75 + cot 15 without using tables.

    10. a) Develop formulas for the following.
    i) tan 2α
    ii) cot 2α

    Thank you!
    Last edited by finalfantasy; October 29th 2007 at 12:10 PM.
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by finalfantasy View Post
    Hi guys! How do you solve this question?

    1. Tan 75 (using the compound angle formulae)
    recall that \tan ( \alpha + \beta) = \frac {\tan \alpha + \tan \beta}{1 - \tan \alpha \tan \beta}

    now, you can write \tan 75 as \tan (45 +30 )

    now apply the formula


    can you continue?



    8. a) Develop formulas for cot(α + β) and cot(α - β).
    b) Find cot 75 + cot 15 without using tables.
    use the fact that \cot ( \alpha + \beta ) = \frac {\cos ( \alpha + \beta) }{\sin ( \alpha + \beta)}

    you know the addition formulas for sine and cosine right?

    10. a) Develop formulas for the following.
    i) tan 2α
    ii) cot 2α

    Thank you!
    again, write \tan 2a as \frac {\sin 2a}{\cos 2a}

    and \cot 2a as \frac {\cos 2a}{\sin 2a}

    and apply the double angle formulas for sine and cosine
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  3. #3
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    hmm ... I tried doing tan (45 + 30) and attempted to solve it, but i kept getting the wrong answer!
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