Re: a question about complex variable

*To*: mathgroup at smc.vnet.net*Subject*: [mg21661] Re: [mg21620] a question about complex variable*From*: "Richard Finley" <rfinley at medicine.umsmed.edu>*Date*: Fri, 21 Jan 2000 04:00:12 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Try the following: In[1]:= FullSimplify[Abs[C], Im[P]==0] Out[1]:= Abs[Tan[A]] as it should. Look in the Mathematica help or book for a description of the Arg[z] function....it returns unevaluated unless z is numeric. Regards, RF >>> ZHU Xiaopeng <xpzhu at red.semi.ac.cn> 01/18/00 01:35AM >>> In my algebra computation, I obtain a expression: C = (- I Cos[2 P] - Sin[2 P]) Tan[A] P,A are real variables. Apperently, the argument of C is -2(P+Pi/4) and the absolute value of C is Tan[A]. But when I use Arg[C] and Abs[C], Mathematica tells me: Out[41]=Abs[(-I Cos[2 P] - Sin[2 P]) Tan[A]] Out[42]=Arg[(-I Cos[2 P] - Sin[2 P]) Tan[A]] This problem appeared at beginning of the computation. I have no idea to deal with it, so the expressions become longer and longer during the computation. Can somebody help me?