# Clear up some cross product confusion for me

by 2slowtogofast
Tags: clear, confusion, cross, product
 P: 123 Here is what I have A=xro+yr1 B=yro+xr1 I need to find A x B I am confused about do it because The components of A and B are in terms of vectors If A = 3i + 4j + 7k and B = 2i + 2j + 1k I would have no problem (these numbers are meaningless just giving an example) finding A x B but I don't have components I have vectors. Can some one explain how to do this. Thanks
 P: 123 Could I set it up as follows Sorry I don't no how to input a matrix hopefully this can get the idea across ro r1 k ro r1 x y 0 x y y x 0 y x and then do the normal cross product thing where you multiply diagonals and so on. The thing that troubles me is there is really no k component. The only thing I know is my answer will be perpindicular to the plane with r0 and r1 so not sure what to do
 Sci Advisor P: 5,767 AXB = (x2 - y2)r0Xr1. I am assuming x and y are scalars.
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P: 25,457

## Clear up some cross product confusion for me

hi 2slowtogofast!
 Quote by 2slowtogofast Here is what I have A=xro+yr1 B=yro+xr1 I need to find A x B
hints: distributive law
what are ro x ro and r1 x r1 ?
 P: 123 @tinytim roxro = 0 I can see how that will simplify things I am confused about the distributive law part A x (B+D) = (AxB)+(AxD) I have somthing more like this (xro+yr1) x (yro+xr1) = (xro+yr1) x yro + (xro+yr1) x xr1 Use the distributive rule again on the RHS (xro x yro) + (yr1 x yro) + (xro x xr1) + (yr1 x r1) Then the first and last terms are 0. Am on the right track or did I make a wrong turn somewhere
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P: 25,457
hi 2slowtogofast!

(just got up )
 Quote by 2slowtogofast (xro x yro) + (yr1 x yro) + (xro x xr1) + (yr1 x r1) Then the first and last terms are 0. Am on the right track
yes

now what is the relationship between r1 x ro and ro x r1 ?
 P: 123 r0 x r1 = -(r1 x r0) If that is correct i think i can take it from there thanks for the help
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