Let $A$ be a $n\times(n+1)$ matrix, full row rank. Let $\tilde A=A+\Delta A$ be a perturbation of $A$, again with full row rank.
I am interested what is known about bounds on the angle between the kernel $x$ of $A$ ($Ax=0$) and the kernel $\tilde x$ of $\tilde A$ ($\tilde A \tilde x=0$). Namely, a bound on $\frac{x^T\tilde x}{|x||\tilde x|}$.
Could somebody hint me some good literature?