If i have a matrix $W \in \Re^{mxc} $ and a matrix with orthonormal columns $E \in \Re^{nxm}$ and another matrix $B \in \Re^{mxm}$ which is symmetric and positive and where $B=EE^T$ then how could we establish the following equivalence : $(E^TW)^T (E^TW)^T = W^TBW$ ?
Thanks for the help.