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Homework Help: Trigonometry problem

  1. Mar 27, 2015 #1
    1. The problem statement, all variables and given/known data
    The lines L1 and L2 with equations y=2x and 3y=x-1 respectively,are drawn on the same set of axes. Given that the scales are the same on both axes and that the angle L1 and L2 make with the positive x-asis are A and B respectively,

    write down the value of Tan A and the value of Tan B

    2. Relevant equations

    3. The attempt at a solution

    I've figured out tanA which is 2. Why? It doesn't matter what value of x you substitute into L1 you'll always get 2 when you do O which is Y divide by A which is X. I'm using tan=o/a. But, I do not know how to get tan B; it isn't the same thing.
  2. jcsd
  3. Mar 27, 2015 #2


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    The general (or standard) equation for a straight line is y = mx + c where

    m is the slope = Δy/Δx = Tanθ
    and c is a constant.

    So comparing that with y=2x it's clear that m=2 (and c=0).

    I suggest you rearrange the other equation (3y=x-1) into the standard form for a straight line and work out the slope m.
  4. Mar 27, 2015 #3
    Δy/Δx = Tanθ << Ahh you're right. I never noticed even though I used the same method.Silly me. Thanks
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