Find the values of x and y and write vector B. xi+yj * 4i + 2j = -16 How do I find x and y?
Last edited by INeedOfHelp; November 12th 2012 at 11:18 AM.
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Equate the dot product of A and B to -16, and to what should you equate the dot product of B and C? Once you write these products, then you will two equations in x and y.
So... (yj)(2j)+(xi)(4i)= -16 2yj^{2}+4xi^{2} = -16 So far is that right, or no?
I would write: Now, since and are perpendicular, to what will we equate their dot product?
B C <2,1> * <2,3> = (4)+(3) = 7 That's not right, is it? hdfhkfdg
No, that's not right...you are taking the dot product of one half of A and C...you want to use B and C, and set it equal to what?
Equal to 0 because they are orthogonal vectors??
Yes, exactly...good. So what equation results from this?
2x+3y=0 ?
Great! Now, you have: (1) (2) Solve this system to get and .
So would vector B = <-6,4> ?
Yes, great work!
Thank you so much! (:
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