Student Support Forum: 'Abs[z] stays complex, z is constraint' topicStudent Support Forum > General > "Abs[z] stays complex, z is constraint"

 < Previous Comment | Next Comment > Help | Reply To Comment | Reply To Topic
 Author Comment/Response jf 05/28/12 1:56pm Mathematica assumes the variables could be complex. A quick way to say all the variables are Real is to wrap the Abs[..] in ComplexExpand[]/ In[1]:= Abs[1/rf + (ri + x)/(lo^2 w^2 + (ri + x)^2) - I (1/(lm^2 w^2) + (lo^2 w^2)/(lo^2 w^2 + (ri + x)^2))] Out[1]= Abs[1/rf + (ri + x)/(lo^2*w^2 + (ri + x)^2) - I*(1/(lm^2*w^2) + (lo^2*w^2)/(lo^2*w^2 + (ri + x)^2))] In[2]:= ComplexExpand[ Abs[1/rf + (ri + x)/(lo^2 w^2 + (ri + x)^2) - I (1/(lm^2 w^2) + (lo^2 w^2)/(lo^2 w^2 + (ri + x)^2))] ] Out[2]= Sqrt[(-(1/(lm^2*w^2)) - (lo^2*w^2)/(lo^2*w^2 + (ri + x)^2))^2 + (1/rf + (ri + x)/(lo^2*w^2 + (ri + x)^2))^2] In[3]:= \$Version Out[3]= "8.0 for Microsoft Windows (64-bit) (October 7, 2011)" If you check http://reference.wolfram.com/mathematica/ref/Abs.html, under More Information, "Abs[z] is left unevaluated if z is not a numeric quantity." URL: ,

 Subject (listing for 'Abs[z] stays complex, z is constraint') Author Date Posted Abs[z] stays complex, z is constraint Max 05/27/12 8:59pm Re: Abs[z] stays complex, z is constraint jf 05/28/12 1:56pm Re: Re: Abs[z] stays complex, z is constraint Max 05/28/12 2:52pm
 < Previous Comment | Next Comment > Help | Reply To Comment | Reply To Topic