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

• To: mathgroup at smc.vnet.net
• Subject: [mg62632] Re: [mg62589] Built-In fuctions redefined---How?
• From: Bob Hanlon <hanlonr at cox.net>
• Date: Wed, 30 Nov 2005 00:06:11 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

```One approach that only affects the output.

\$Post=(#/.
{Sin[x_Symbol]/;StringLength[ToString[x]]==1:>
ToExpression["s"<>ToString[x]],
Cos[x_Symbol]/;StringLength[ToString[x]]==1:>
ToExpression["c"<>ToString[x]]}&);

expr=Sin[x]^2+Cos[x]^2+Cos[y]-Sin[z]

cx^2 + sx^2 + cy - sz

expr//Simplify

cy - sz + 1

Bob Hanlon

>
> From: Virgil Stokes <virgil.stokes at it.uu.se>
To: mathgroup at smc.vnet.net
> Date: 2005/11/29 Tue AM 04:44:26 EST
> Subject: [mg62632] [mg62589] Built-In fuctions redefined---How?
>
> 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
>
>
>
>
>

```

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