Expression 6: "A" Subscript, "r" "g" , Baseline left parenthesis, "z" , right parenthesis equals left brace, StartAbsoluteValue, left parenthesis, "m" Subscript, "o" "d" , Baseline left parenthesis, "z" , right parenthesis , "a" Subscript, "r" "g" , Baseline left parenthesis, "z" , right parenthesis , right parenthesis , EndAbsoluteValue less than pi : negative StartFraction, "a" Subscript, "r" "g" , Baseline left parenthesis, "z" , right parenthesis Over pi , EndFraction , StartAbsoluteValue, "z" , EndAbsoluteValue equals 1 : left brace, theta Subscript, "z" , Baseline left parenthesis, "z" , right parenthesis equals pi : pi , right brace , right braceArgz=modz,argz<π:−argzπ,z=1:θzz=π:π