# How to remove imaginary parts

1. Jun 20, 2011

### kaizen.moto

Hi all,

I have this expression containing complex numbers and I wanted the expression to be displayed with real parts only. How can i do this?

For instance, the original expression is,

eqn = (16.0001+3.16141*10^-21 i)-(0.00860351-1.16927*10^-18 i) Ao[1]+(0.00537811-4.47536*10^-19 i) Ao[2]+(0.00220452-3.26709*10^-19 i) Ao[3]+(0.000739715-4.06632*10^-19 i) Ao[4]+(0.00013763-7.3495*10^-20 i) Ao[5]+(0.0000531553-2.41817*10^-20 i) Ao[6]+(0.0000215401-7.71228*10^-21 i) Ao[7]+(8.33787*10^-6-2.34411*10^-21 i) Ao[8]+(3.04878*10^-6-6.62795*10^-22 i) Ao[9]+(1.05209*10^-6-1.65167*10^-22 i) Ao[10]+(3.41169*10^-7-3.05161*10^-23 i) Ao[11]+(1.03042*10^-7-4.88271*10^-25 i) Ao[12]+(2.84435*10^-8+1.99951*10^-24 i) Ao[13]+(1.97033*10^-9-1.78568*10^-25 i) Ao[14]-(1.27252*10^-9-2.32126*10^-24 i) Ao[15]+(1.48923*10^-9+1.28512*10^-24 i) Ao[16]+(2.6173*10^-9+5.15919*10^-24 i) Ao[17]-(0.00140526-1.73272*10^-18 i) Bo[1]-(0.00102695-5.8933*10^-20 i) Bo[2]-(0.00120414-4.97092*10^-19 i) Bo[3]-(0.000925213+9.831*10^-19 i) Bo[4]-(0.000299566+1.36884*10^-21 i) Bo[5]-(0.000114259-2.87861*10^-22 i) Bo[6]-(0.0000407664-5.94754*10^-22 i) Bo[7]-(0.0000136803-4.09024*10^-22 i) Bo[8]-(4.28978*10^-6-2.03871*10^-22 i) Bo[9]-(1.23214*10^-6-8.23679*10^-23 i) Bo[10]-(3.08143*10^-7-2.67666*10^-23 i) Bo[11]-(5.67061*10^-8-5.63015*10^-24 i) Bo[12]-(1.24165*10^-9+3.89669*10^-25 i) Bo[13]+(1.79991*10^-9-2.12938*10^-24 i) Bo[14]+(2.8092*10^-9-5.68199*10^-24 i) Bo[15]+(6.17782*10^-9-8.51869*10^-24 i) Bo[16]+(4.60098*10^-9+5.81194*10^-24 i) Bo[17].

I have tried to various methods but still failed including Re[eqn] etc etc etc.

2. Jun 20, 2011

### Hurkyl

Staff Emeritus
Did you try to FullSimplify that? You might need to tell FullSimplify that the Ao's and Bo's are real. (They are real, right?)

You could probably tell Mathematica to reduce the precision.

You could repeat the derivation in a way that doesn't use complex numbers.

You could use one of the formulas for computing the real part of a number.

You could tell it to replace i with 0.

You could find a way to do whatever you wanted to do next that doesn't require the coefficients to be real.

3. Jun 20, 2011

Chop[eqn]