Linear mapping/Eigenvalue 1 and -1/Remark

Beside the eigenspace for ${}0\in K$, which is the kernel of the linear mapping, the eigenvalues ${}1$ and ${}-1$ are in particular interesting. The eigenspace for ${}1$ consists of all vectors which are sent to themselves. Restricted to this linear subspace, the mapping is just the identity, it is called the fixed space. The eigenspace for ${}-1$ consists in all vector which are sent to their negative. On this linear subspace, the mapping acts like the reflection at the origin.