for a11, a12, a13, a21, a22, a23, a31, a32, a33, b11, b12, b13, b21, b22, b23, b31, b32, b33 being Element of F_Real
for A, B being Matrix of 3,F_Real st A = <*<*a11,a12,a13*>,<*a21,a22,a23*>,<*a31,a32,a33*>*> & B = <*<*b11,b12,b13*>,<*b21,b22,b23*>,<*b31,b32,b33*>*> holds
A * B = <*<*(((a11 * b11) + (a12 * b21)) + (a13 * b31)),(((a11 * b12) + (a12 * b22)) + (a13 * b32)),(((a11 * b13) + (a12 * b23)) + (a13 * b33))*>,<*(((a21 * b11) + (a22 * b21)) + (a23 * b31)),(((a21 * b12) + (a22 * b22)) + (a23 * b32)),(((a21 * b13) + (a22 * b23)) + (a23 * b33))*>,<*(((a31 * b11) + (a32 * b21)) + (a33 * b31)),(((a31 * b12) + (a32 * b22)) + (a33 * b32)),(((a31 * b13) + (a32 * b23)) + (a33 * b33))*>*>