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Math Help - Soh-cah-toa

  1. #1
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    Soh-cah-toa

    This should be easy, but every time i type it in, i get the wrong answer! Please tell me what i am doing wrong!


    Suppose is an angle in the second quadrant and


    Then what is

    and
    .
    And what is:


    Answer in degrees and radians please!
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by MathNeedy18 View Post
    This should be easy, but every time i type it in, i get the wrong answer! Please tell me what i am doing wrong!


    Suppose is an angle in the second quadrant and


    Then what is

    and
    .
    And what is:


    Answer in degrees and radians please!
    so first thing you do is draw your triangle (if you want to use that method, you can also use trig identities to do it--i'll show you if you're interested)

    so now, our right-triangle has an acute angle called u, with the opposite side, length 2, the hypotenuse, length 3, and the other side, length sqrt(5) (by pythagoras' theorem).

    so cos(u) = adj/hyp = sqrt(5)/3 ...but wait, we are in the second quadrant, cosine is negative. so cosu = - sqrt(5)/3

    the tangent is also negative in the second quad. so
    tanu = - opp/adj = - 2/sqrt(5)

    and we have:

    u = arcsin(2/3) = 41.8103149 degrees = 0.729727656 radians


    This is my 14 th post!!!!
    Last edited by Jhevon; April 25th 2007 at 05:31 PM.
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  3. #3
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    THANKS SOO MUCH! I forgot to put a negative sign!
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