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Vector question

  1. Aug 8, 2008 #1
    How do you find the components of this vector:

    Magnitude 15, angle 315

    Thanks!
     
  2. jcsd
  3. Aug 8, 2008 #2
    How do you find the components of this vector:

    Magnitude 15, angle 315

    Thanks!
     
  4. Aug 8, 2008 #3

    mathman

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    Your question seems to imply a 2-d vector.

    x=15cos(315)
    y=15sin(315)
     
  5. Aug 8, 2008 #4

    tiny-tim

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    Welcome to PF!

    Hi robfrech! Welcome to PF! :smile:

    Draw a diagram, including the x and y axes.

    Then use trigonometry to find the x and y coordinates … taking care to use a minus sign where appropriate! :smile:
     
  6. Aug 8, 2008 #5

    chroot

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    Draw a picture and consider the resulting triangle. You know the length of the hypotenuse, and two of the angles. Use trigonometry to find the other sides.

    - Warren
     
  7. Aug 8, 2008 #6
    How do you draw a triangle with a 315 degree angle?
     
  8. Aug 8, 2008 #7

    HallsofIvy

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    Well, first you should have specified where the angle is measured from!

    The convention is that the angle is measured from the positive x-axis so I will assume that. Now 315= 360- 45 so you have a a point in the 4th quadrant with x-coordinate positive and y-coordinate negative. The triangle itself has hypotenuse 15, angle 45 degrees. x= 15 cos(45), y= -sin(45). Since cos(315)= cos(45) and sin(315)= -sin(45), that is exactly what mathman said originally.
     
  9. Aug 8, 2008 #8

    chroot

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    Draw two crossed lines, representing the x and y axes. Draw a circle centered on the origin. Count 315 degrees around the circle, counterclockwise, starting from the point where the circle meets the positive x-axis. The point is in the lower-right quadrant. Draw two lines: one from the origin to the point, the other from the x-axis to the point. The second line should make a right angle with the x-axis.

    You've now created a triangle. You know one angle and two sides. You can solve for the others.

    - Warren
     
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