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Above-Below test

  1. Mar 1, 2007 #1
    Hi;
    If I have a line L1 first end point of L1(a1,a2,a3) and the second end point of L1(b1,b2,b3) in 3-dimensions.
    From them I could get the eqaution of the line in 3-dimensions which is :
    (X-a1/b1)=(y-a2/b2)=(z-a3/b3) if it is wrong please do let me know
    I have an example:
    first end point of L1(2,0,0) & the second end point of L1(-2,0,0)
    note:(a1,a2,a3) for the first end point and (b1,b2,b3) for the second end point
    I want to test the point(2,-2,2)(which refers to (x,y,z)) if it is above or below the line L1
    so I pluged in the values in the above eqaution and I got negative sign ,I tried another point which is on the other side(-2,2,-2) but it gave negative sign which means I have something wrong could you please help me in this?


    Thanks
    totototo
     
  2. jcsd
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