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# C4 Vectors watch

1. Not sure how to do this:

with respect to the origin O, the position vectors of the points L and M are
2i -3j +3k and 5i + j + ck respectively, where c is a constant.

The point N is such that OLMN is a rectangle.

a) write down the value for c.

many thanks.
2. I'm not 100% but from what I remember of vectors, could you use the scalar product and make it equal to 0 (when L and M are perpendicular)

10 - 3 - 3c = 0?
c = -7/3
3. (Original post by jenny0502)
I'm not 100% but from what I remember of vectors, could you use the scalar product and make it equal to 0 (when L and M are perpendicular)

10 - 3 - 3c = 0?
c = -7/3
Method's right. Think you made a small slip with a minus sign but otherwise yeah.
4. ahh.. yup

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Updated: March 13, 2008
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