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Homework Help: Finding the x and y components of this vector

  1. Sep 12, 2010 #1
    Hey guys,

    I am not sure I did this problem correctly and would like some feedback. Below is how I reasoned through the problem. Thanks for your help.


    1. The problem statement, all variables and given/known data

    Find x- and y-components of the vector (3.0 , - x-direction).

    2. Relevant equations
    cosθ= A/H
    sinθ= O/H

    H= -3.0

    3. The attempt at a solution

    I made two vectors connecting to form a 90 degree angle pointing at the hypotenuse. The other two angles are now 45 degrees and I plugged them in to the above equations as follows:
    cos(45)=A/-3 = -2.12
    sin (45)=O/-3= -2.12

    (-2.12)^2 + (-2.12)^2 = -3^2
    8.99 or 9 = 9
    So X and Y are both -2.12
  2. jcsd
  3. Sep 12, 2010 #2


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    Am I correct in reading that your original vector looks like this:

    3 <----------------+


    If so, I dont see much of a y-component.
  4. Sep 12, 2010 #3
    yes. But isn't that the resultant vector? I solved two other prior to this question and they gave a magnitude and direction. To solve those, I made two vectors and solved for their side of the triangle. Is that not how I should be trying to solve this question? At first I thought it would be 0, but it's not, at least to my understanding, asking for the x and y coordinates of the line drawn above
  5. Sep 12, 2010 #4


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    This problem is a special case where the direction lies exactly along one of the axes, in which case there is no right triangle for you to construct. So your trig functions don't apply.
  6. Sep 12, 2010 #5
    So does that mean x= -3 and y=0?
  7. Sep 12, 2010 #6


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    That sounds right to me! Good luck with your coursework.
  8. Sep 12, 2010 #7
    Thanks for your help!
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