#Finding Dimension of F intersection with G

9 messages · Page 1 of 1 (latest)

stone comet
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Would an appropriate approach be calculating the rank of the matrix, with columns being the 5 respective vectors?
Using mathematica, I computed it to be of rank 3. Thus the dimension of F intersection with G is 3?

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stone comet
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The written question in the pic, asks for finding Dim(F+G), however I just wanna make sure I'm finding Dim(F intersection G ) correctly

limpid tiger
# stone comet Would an appropriate approach be calculating the rank of the matrix, with column...

Well you already have your answer take a vectorial space E if you take two subspaces F and G then F+G={x in E such that there exist two vectors y and z in F and G such that x=y+z} so if you consider that F and G are both finite dimension then take (ei) a basis of F and (fi) one of G then for any x in F+G ( dim(F)=p dim(G)=k)x=y+z with y and z in F and G respectively so if y=y1e1+…+ypep and z=z1f1+…+zkfk then you have x=y1e1+…+ypep+z1f1+…+zkfk and if one or more of the elements of the basis of G is a linear combination of the basis of F then the basis of F+G is the basically the set of vectors that generates both basis so basically it has the same cardinal as the rank of both family of vectors combined

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And here using Grassmans formula you’d see that the dimension of F inter G is actually the dimension of the kernel of your matrice

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(Rank theorem)

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To conclude here the rank of the matrice is the answer

stone comet
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Much appreciated! @limpid tiger