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1. 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.

2. what's Q?
3. Q is the point where the two lines intersect, worked it out earlier in the question to be (2,5,4)
4. (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.

hm.. for some reason i get a different value of lambda
5. (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.

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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