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    A question gives the equations of 2 lines
    l1: r = i + 3j + 5k + lamda(i +2j - k)
    l2: r = 2i + 3j - 4k + mew(2i + j + 4k)

    Ive already worked out that lamda is 1 and mew is 2 and that the lines are perpendicular

    But now it says "the point P with x co-ordinate 3 lies on l1 and the point R with x co-ordinate 4 lies on the line l2" and I dont know how to put this information into the vectors so that I can find the area of the triange PQR.

    Please help! Thanks x
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    what's Q?
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    Q is the point where the two lines intersect, worked it out earlier in the question to be (2,5,4)
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    (Original post by jazzyj)
    A question gives the equations of 2 lines
    l1: r = i + 3j + 5k + lamda(i +2j - k)
    l2: r = 2i + 3j - 4k + mew(2i + j + 4k)

    Ive already worked out that lamda is 1 and mew is 2 and that the lines are perpendicular

    But now it says "the point P with x co-ordinate 3 lies on l1 and the point R with x co-ordinate 4 lies on the line l2" and I dont know how to put this information into the vectors so that I can find the area of the triange PQR.

    Please help! Thanks x
    hm.. for some reason i get a different value of lambda :confused:
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    (Original post by jazzyj)
    A question gives the equations of 2 lines
    l1: r = i + 3j + 5k + lamda(i +2j - k)
    l2: r = 2i + 3j - 4k + mew(2i + j + 4k)

    Ive already worked out that lamda is 1 and mew is 2 and that the lines are perpendicular

    But now it says "the point P with x co-ordinate 3 lies on l1 and the point R with x co-ordinate 4 lies on the line l2" and I dont know how to put this information into the vectors so that I can find the area of the triange PQR.

    Please help! Thanks x
    work out the position vector of the point on line |1 when x=3,and the same for |2 when x=4.And u also have Q so then u can work out the area.
    And for |1 when x=3 then u know that 1+lambda=3.
 
 
 
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