Need help to prove (or disprove, hope not) this result:
Let Q=[q_ij] be a orthogonal matrix (Q^T*Q=Identity) and let Q2 be the matrix of the squares of the entries of Q, that is Q2=[q^2_ij]. I need to prove that Q2 is nonsingular.
Been trying with some results about the Hadamard or Schur...