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Math Help - Trigonometry

  1. #1
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    Dec 2007
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    Trigonometry

    Hi. I have the triangle PQR pq=17cm , qr=15cm and pr=8cm

    I need to write down the values of sinQ,cos Q and tan Q. I know the soh,cah,toa rules but not sure how to apply them. Thank you.

    Also i need to sketch curves such as y=sin x for 0degrees <and equal to x <and equal to 360degrees. then solve the equation sin x=0.5 for 0degree <and equa to x <and equal to 360 degree then illustrate these on the sketch.

    I have only just started this subject and this is a beginner exercise before we begin the main lessons into it, so i would be grateful for any guidence you can give.

    Thank you
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  2. #2
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    Lexington, MA (USA)
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    Hello, Chez!

    Ha! . . . I mislabelled my diagram!


    I have the triangle PQR: . PQ=17\text{ cm, }\:QR=15\text{ cm, and }\:PR=8\text{ cm}

    Find: . \sin Q,\;\cos Q,\;\tan Q
    Code:
        P *
          |  *
          |     *   17
        8 |        *
          |           *
          |              *
        R * - - - - - - - - * Q
                  15

    Note that: . 8^2 + 15^2 \:=\:17^2
    . . The sides satisfy the Pythgorean Theorem.

    Hence, \Delta PQR is a right triangle.


    Therefore:

    . . \begin{array}{ccccc}\sin Q & = &\dfrac{8}{17} \\ \\[-2mm] \cos Q & = & \dfrac{15}{17} \\ \\[-2mm] \tan Q & = & \dfrac{8}{15} \end{array}\quad \hdots . corrected

    Last edited by Soroban; March 15th 2008 at 05:31 PM.
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  3. #3
    Member
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    Dec 2007
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    I did the pythagorous thery at the beginning
    to find the sin etc the questions says the keep the answer as a fraction, so it cant be a whole number..
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