# Linear Algebra: dimension of subspace question

## Homework Statement

Find an example of subspaces W1 and W2 in R^3 with dimensions m and n, where m>n>0, such that dim(intersection of W1 and W2)= n

## Homework Equations

dim(W1+W2)= dim(W1) + dim(W2)-dim(intersection of W1 and W2)

## The Attempt at a Solution

Well what I know for sure is that I have to use the equation dim(W1+W2)= dim(W1) + dim(W2)-dim(intersection of W1 and W2). I'm just really confused on how the subspaces should be. Should they maybe be matrices?

## The Attempt at a Solution

Dick
Homework Helper
Subspaces are spans of sets of vectors. If you are working in R^3 then your only choice to make m>n>0 is m=2 and n=1, right? Pick the standard basis, e1=(1,0,0), e2=(0,1,0), e3=(0,0,1). One subspace with dimension 2 is span(e1,e2). A subspace with dimension 1 is span(e1). Do you have any idea what I'm talking about?? Do you know what a span is? Your question about whether the answer is a matrix makes me think we should start from the basics.

lol, yeah I know what you are talking about. I'm just really lost with this stuff right now. thanks man.

Dick