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Math Help - Math 11 connecting coordinate and plane geometry

  1. #1
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    Math 11 connecting coordinate and plane geometry

    The sides of a triangle have equations:
    y=5/4x+21/4, y=-3/4x+13/4 and y=1/4x+1/4
    Prove it is not a right triangle, and state what type of triangle it is.

    -I know that it is not a right triangle by looking at the slopes in the equations, neither is a negative reciprocal of the other making them perpendicular. Im assuming it is scalene by looking at the y-intersept. I dont remember how to convert the equation from slope intercet form into coordinates.Im assuming i have to find the distance between each point im just not sure how to break the equation down, please help.
    Thank you
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  2. #2
    Senior Member nikhil's Avatar
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    for finding individual points
    let given equations be A,B and C.now solve simultaneously equation AB,BC and CA. this will give you point of intersection of lines and hence coordinates of vertices. then by distance formula you can easily find the length of individual side
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  3. #3
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    Did you graph all three lines?
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    I know this might seem really stupid but i cant remember how to get the coordinates from the slope intercept form... I know how to get the distance once i have those, im having a brain block.
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  5. #5
    Senior Member nikhil's Avatar
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    Quote Originally Posted by missionmom View Post
    I know this might seem really stupid but i cant remember how to get the coordinates from the slope intercept form... I know how to get the distance once i have those, im having a brain block.
    slope intercept form is y=mx+c
    single equation can not give you the coordinate of vertices of a triangle.To get coordinates of vertices you will have to solve equations simultaneously as I mentioned before. other not so good method is to plot the graph and find points of intersection
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  6. #6
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    I dont remember how to find the verticles. I know I cant get them from one equation, i just dont remember what type of formula to use to find them, i know i will have to use two equations. Im so stuck! please explain...
    I graphed the equations and assume the points a(-1,4) b(-5,-1) c(3,1) I just thought there was a formula way to solve the coordinates so i was sure i got the right verticles??? Im new at this...
    Last edited by missionmom; August 27th 2009 at 10:08 AM.
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  7. #7
    Senior Member nikhil's Avatar
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    Lightbulb check this out

    y=(5/4)x+21/4.........equation 1
    y=(-3/4)x+13/4.........equation 2
    subtracting equation 2 from equation 1 we get
    2x+2=0 or x=-1
    by putting this value in equation 1 we get
    y=4
    so coordinate of one of the vertices is (-1,4).similarly you can find coordinates of other vertices.
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  8. #8
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    Thank you, now I remember. I just wanted to make sure that if i couldnt see what the points were i could do it algebraiclly. Thank you.
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