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Homework Help: Find the x and y components of the following displacement.

  1. Nov 22, 2009 #1
    1. The problem statement, all variables and given/known data
    20m 52deg W of N

    2. Relevant equations
    trig functions

    3. The attempt at a solution
    I got 20cos52=12.3m west
    and 20sin52=15.8m north

    yet the answer in the book says 12.3m north and 15.8m west. I don't understand...I thought cos was the x component and sin was the y component. so 15.8 m north is y and 12.3m west is x no? Please help me understand how the triangle and its components would look so i may recreate on paper?
    Thank you.
  2. jcsd
  3. Nov 22, 2009 #2
    The angle is 52 degrees west of north. So you start at north and rotate 52 degrees to the left. The triangle will look similar to this:

    Code (Text):
    Angle B -> |\
               | \
               |__\ <- Angle A
    Angle A is 38* and Angle B is 52*.

    Hope this helps.
  4. Nov 22, 2009 #3
    I thought angle A would be 52*
  5. Nov 22, 2009 #4
    Take a look at this:


    The angle 52* West of North results in line c (note that in my pretty drawing, angle C and side c have no relation). Angle C is 52*, and since the axis are perpindicular, angle A + angle C needs to equal 90*, so A is equal to 38*.

    So then cos(A) = b / c -> b = c * cos(A)
    and, sin(A) = a / c -> a = c * cos(A)
  6. Nov 22, 2009 #5
    I figured it out a different way, but thank you for the help anyway.
    I got Ry/20=cos52* so Ry=20cos52*=12.3m north
    I got Rx/20=sin52* so Rx=20sin52* =15.8m west
  7. Nov 22, 2009 #6
    how do i get graphics like that to draw triangles etc?
  8. Nov 22, 2009 #7
    I just used paint.
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