Re: Newby Q: How to specify reals

• To: mathgroup at smc.vnet.net
• Subject: [mg110579] Re: Newby Q: How to specify reals
• From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
• Date: Sat, 26 Jun 2010 03:11:40 -0400 (EDT)

```On 25 Jun 2010, at 20:28, David Park wrote:

> Maybe ComplexExpand should have been called ComplexSimplify or ComplexReduce
> - but it's too late now and I don't know if that, in itself, would alleviate
> the problem for beginners.

But, as has been pointed out many times, it *does" expand. How would ComplexSImplify and ComplexReduce fit with the following behaviour:

In[63]:== ComplexExpand[(a + b)^3]

Out[63]== a^3 + 3*a^2*b + 3*a*b^2 + b^3

ComplexExpand[(a + b)*(c + d)]

a*c + a*d + b*c + b*d

Is this reduction? Is is simplification? It's clearly *expansion* as it this:

ComplexExpand[z, {z}]

Re(z)+I Im(z)

and this

ComplexExpand[z, {z}, TargetFunctions -> {Arg, Abs}]

Abs[z]*Cos[Arg[z]] + I*Abs[z]*Sin[Arg[z]]

In fact, I don't think there is any other name but ComplexExpand or something synonymous that fits this and all other behaviour of ComplexExpand. To say that it "should have been called something else" is actually misleading.

Andrzej Kozlowski

```

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