Saltire detected the symbol, which often appears with balls in the quadrants formed by the arms of the chi-cross, in standards that appear on the coins of Persepolis. She suggested that early Christians endorsed its solar symbolism as appropriate to Christ. She also wrote: "although it cannot be proved, ... in the white saltire of St. Andrew we still have a reminiscence of the old standard of the Persepolitan kingdom". In the old European Union standard, a black saltire set in an orange square is the hazard symbol for irritants (Xi) or harmful chemicals (Xn). It indicates a hazard less severe
Square root of a matrix but if the process converges, the matrix formula_26 converges quadratically to a square root , while formula_27 converges to its inverse, . Yet another iterative method is obtained by taking the well-known formula of the Babylonian method for computing the square root of a real number, and applying it to matrices. Let "X" = "I", where "I" is the identity matrix. The iteration is defined by Again, convergence is not guaranteed, but if the process converges, the matrix formula_29 converges quadratically to a square root "A". Compared to Denman–Beavers iteration, an advantage of the Babylonian method is that only one