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Homework Help: Angle of Inclination of Line in Vector Equation

  1. May 25, 2010 #1
    1. The problem statement, all variables and given/known data
    Find the angle of inclination of each of the following lines.
    i) r = (2,-6) + t(3,-4) ii) r = (6,1) + t(5,1)

    B) prove that the tangent of the angle of inclination is equal to the slope of the line.


    2. Relevant equations
    N/A

    3. The attempt at a solution
    I know that the angle ø, 0° < ø < 180°, that a line makes with the positive x-axis is called the angle of inclination of the line. However, I don't have any idea how to approach this question.
     
  2. jcsd
  3. May 25, 2010 #2

    rock.freak667

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    Well your lines are in the xy-plane.
    So why don't you draw the lines and find the angle using some trigonometry?

    OR you can find the dot product with a unit vector in the direction of the x-axis <1,0>
     
  4. May 25, 2010 #3
    How do find the solution without having to draw the lines?
     
  5. May 25, 2010 #4

    rock.freak667

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    the dot product of the direction of the vector line and the unit vector in the direction of the x-axis will give you the angle.
     
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