Okay, so here's the question:

L1:[ 1 2 1 ]^T +s[ 2 -1 1 ] ^T

L2: [ 3 0 1 ]^T +t[ 1 1 2 ]^T

I need to find where they intersect and the cos of the acute angle theta between the lines.

I was thinking of trying to put them into matrices and then trying to equate them, but I don't really know if that's allowed.

I was thinking

L1=[-2 1

1 2

-1 1]

And

L2= [-1 3

-1 0

-2 1]

I was hoping L2-L1 would equal 0, but I have a feeling this is wrong because L1 has the parameter s and L2 has the parameter t.

Any hints are appreciated!