Orthogonally diagonalize the matrix by finding an orthogonal matrix Q and a diagonal matrix D such that Q^TAQ = D. (Enter each matrix in the form [[row 1], [row 2], ...], where each row is a comma-separated list.)
A = [[6, sqrt(7)], [sqrt(7), 0]]
(D, Q) = ( [[-1, 0], [0, 7]], [[-1/sqrt(7), sqrt(7)], [1, 1]] )