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Homework Help: Finding trig values given a line

  1. Jul 22, 2012 #1
    1. The problem statement, all variables and given/known data

    The terminal side of angle θ in standard position lies on the given line in the given quadrant. Find sin θ, cos θ, and tan θ.

    2. Relevant equations

    3x + 7y = 0; quadrant III

    3. The attempt at a solution

    The line does not go through the third quadrant. The course instructor commented on this problem. I think he said to drop a line in the second quadrant instead, then to treat the sides of the triangle as if the triangle was in the third quadrant. I'm not sure what side lengths to use though and the relationship between the line, second, and third quadrant is not yet clear to me.
  2. jcsd
  3. Jul 22, 2012 #2
    If I solve for y, I get -3x/7 = y, giving me side lengths 3 and 7 in quadrant II. using Pythagorean theorem, I get sqrt (58) for the hypotenuse.

    for quadrant 3:

    sin θ = -3sqrt(58)/58
    cos θ = -7sqrt(58)/58
    tan θ = 3/7

    Is this correct?
  4. Jul 22, 2012 #3
    They look correct to me.
    It's a weird question though.
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