I think the problem is that you think that a complex number is a vector - it isn't, a complex number is a scalar. And if you multiply a complex number with argument 1° with another with argument 91° you a a complex number with argument 92° (thats the value of your variable rho).
In the last part of your file you had set up true vectors and it worked. But you cannot apply arg() to vectors, the argument of arg has to be a (complex) number.