Morning all, I am having difficulties doing these two question so if you could be kind enough to offer me some help it would be greatly appreciated.

1,Prove that a linear operator on R^2 is a reflection iff it's eigenvalues are -1 and 1, and the eigenvectors associated with these eigenvalues are orthogonal.

2 Prove that a conjugate of a glide reflection in M is a glide reflection and prove that the glide vectors have the same length.

Thanks to all for any help you give.