How can I find a vector perpendicular to a vector I have in two dimensions? I know that the cross product does such thing given two vectors in three dimensions, but how can I find one simply perpendicular to another one in two dimensions?

(-y, x) or (y, -x)

I suppose I should've been more specific. If I have an arbitrary two dimensional vector, is there a way to find the vector perpendicular to it?

(-y, x) or (y, -x)

My mistake. I didn't fully realize you switched the y and x into the other's position. I guess I'm a little tired. Thanks.