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Math Help - Equation of line HELP!

  1. #1
    studiers
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    Question Equation of line HELP!

    How do I work out.......

    Find the equation of a straightline that makes an angle of 55 degrees with the negative X axis and cuts through (2,0)


    and


    Find the equation that runs perpendicular to 2x + 3y = 12 and cuts through the X axis at 2.


    Thanks
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  2. #2
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    Quote Originally Posted by studiers View Post
    How do I work out.......

    Find the equation of a straightline that makes an angle of 55 degrees with the negative X axis and cuts through (2,0)
    You can determine a non-vertical line with a slope and point on it.

    A point on it is (2,0) and the slope is m=tan55.

    Use formula,
    y-y_0=m(x-x_0)
    y=tan55(x-2)
    Simplify.
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  3. #3
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    Hello, studiers!

    Exactly where is your difficulty?

    Do you know the "Point-Slope Formula"?

    Given a point (x
    1,y1) on the line and the slope of the line m,

    . . the equation is: . y - y
    1 .= .m(x - x1)


    Assuming you're new to this material, I'll take baby-steps . . .


    Find the equation of a straight line that makes an angle of 55°
    with the negative x-axis and cuts through (2,0)
    Code:
              * |
                *
                | *
                |   *
                |     *
                |   55° * 125°
          - - - + - - - - * - - -
                |         2 *
                |             *
    The line make an angle of θ = 125° with the positive x-axis.

    Since slope is given by: .m = tanθ, we have: .m = tan125°


    Point-Slope Formula: . y - 0 .= .tan125°(x - 2) . . y .= .(tan125°)x - 2·tan125°



    Find the equation that is perpendicular to 2x + 3y = 12
    and cuts through the x-axis at 2.
    We are given: .2x + 3y .= .12 . . y .= .(-2/3)x + 4

    The line has slope: -2/3
    The slope perpendicular to it is: .m = 3/2

    The line through (2,0) with slope m = 3/2 is:

    . . y - 0 .= .(3/2)(x - 2) . . y .= .(3/2)x - 3

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