# Do projections of lines which are not perpendicular correspond to FLTs?

1. Jul 31, 2012

### imurme8

A math question about projections of lines: Say we have two straight lines which we consider as number lines ($\mathbb{R}$). I've learned that a projection of one line onto another is of the form $ax + b$ for $a,b\in \mathbb{R}$ when the two lines are parallel. If we allow the possibility that the lines are perpendicular, we have a fractional linear transformation of the form $\frac{ax+b}{cx+d}$.

Now if the lines are neither perpendicular nor parallel, do we still have a fractional linear transformation? I've been trying to build such a projection out of projections I know but with no success.