### 2.43.10 Basis of the intersection of two subspaces : `ibasis`

`ibasis` takes as argument two lists of vectors generating
two subspaces of ℝ^{n}.

`ibasis` returns a list of vectors that is a basis of the
intersection of these two subspaces.

Input :

`ibasis([[1,2]],[[2,4]])`

Output :

`[[1,2]]`