       Re: Built-In fuctions redefined---How?

• To: mathgroup at smc.vnet.net
• Subject: [mg62641] Re: Built-In fuctions redefined---How?
• From: Peter Pein <petsie at dordos.net>
• Date: Wed, 30 Nov 2005 00:06:27 -0500 (EST)
• References: <dmh92m\$8rj\$1@smc.vnet.net> <dmhfbi\$bf4\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Peter Pein schrieb:
> Virgil Stokes schrieb:
>> How can I introduce the following definitions:
>>
>>     cx for Cos[x]
>>   sx for Sin[x]
>>
>> where, the argument x, will always be a single symbol, and then still be
>> able to use the trigonometric identities associated with Sin, Cos; e.g.,
>>
>>   cx^2 + sx^2 = 1
>>
>> Note, this is not  c x (3 symbol expression); but,  cx (2 symbol
>> expression).
>> Why? Because I have some rather large matrices with many elements that
>> contain expressions in Cos and Sin terms that make printing and
>> displaying messy and using the MatrixForm can give truncation in the
>> printed output.
>>
>> --V. Stokes
>>
>>
>>
>
> Hi!
>
> Use Format:
>
>
> In:=
> Unprotect[Cos, Sin];
> Format[Cos[x_] := "c" <> ToString[x]];
> Format[Sin[x_] := "s" <> ToString[x]];
>
> In:=
> Expand[(Cos[x] + Sin[t])^3]
> Out= "cx"^3 + 3*"cx"^2*"st" + 3*"cx"*"st"^2 + "st"^3
>
> In:= TrigExpand[% /. t -> x]
> Out= 1 + 2*"cx"*"sx"
>
> Peter
>
Something went terribly wrong: The above Mathematica-lines should read
In:=
Unprotect[Cos,Sin];
Format[Cos[x_]]:="c"<>ToString[x];
Format[Sin[x_]]:="s"<>ToString[x];
Expand[(Cos[x]+Sin[t])^2]
Out= "cx"^2 + 2*"cx"*"st" + "st"^2

In/Out are correct.

Peter

```

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