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Math Help - Trigonometric Functions

  1. #1
    Junior Member
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    Trigonometric Functions

    10. and are acute angles in quadrant I, with sin =7/25 and cos=5/13. Without using a calculator determine the values of sin( + ) and tan( + ).

    So far i did

    x^2 + y^2 = r^2

    x^2 + 7^2 = 25^2

    x^2= 625-49
    x= +- 24

    im not sure if thats even right...
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  2. #2
    Super Member bigwave's Avatar
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    Quote Originally Posted by Skoz View Post
    10. and are acute angles in quadrant I, with sin =7/25 and cos=5/13. Without using a calculator determine the values of sin( + ) and tan( + ).

    So far i did

    x^2 + y^2 = r^2

    x^2 + 7^2 = 25^2

    x^2= 625-49
    x= +- 24

    im not sure if thats even right...
    looks ok so far 24 is the adj side angle \alpha
    looks like you need to use the sum formulas

    cos\alpha = \frac{24}{25} and sin\beta = \frac{12}{5}

    sin(\alpha + \beta) = sin\alpha cos\beta + cos\alpha sin\beta

    Tan\alpha  =  \frac{7}{24}

    Tan\beta = \frac{12}{5}

    tan(\alpha  + \beta) = \frac{tan\alpha  + Tan\beta}{1 - tan\alpha tan\beta}
    Last edited by bigwave; December 1st 2009 at 04:34 PM.
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