       Re: Avoid the use of certain functions

• To: mathgroup at smc.vnet.net
• Subject: [mg111097] Re: Avoid the use of certain functions
• From: David Bailey <dave at removedbailey.co.uk>
• Date: Tue, 20 Jul 2010 03:43:30 -0400 (EDT)
• References: <i1s6vo\$a39\$1@smc.vnet.net>

```On 17/07/10 13:16, Sam Takoy wrote:
> Hi,
>
> Is there a way to ask Mathematica to avoid expressing answers in terms
> of certain functions. For example, I can stand Sec, Csc, Sech, and Csch
> and would rather see Sec^-1, etc.
>
> Thanks!
>

Your description is a bit confused, but I take it you would like to see
an expression output in terms of Sin rather than Csc, but the normal
evaluation process defeats you:

In:= 1/Sin[x]

Out= Csc[x]

One answer to this, is to make a replacement that uses your own function
- say sin[x] for which Mathematica knows nothing. So for example:

In:= Csc[x]^3 /. Csc[z_] -> 1/sin[z]

Out= 1/sin[x]^3

If you need to re-input such expressions, you can use another
transformation to replace sin with Sin.

BTW, if you do a lot of this sort of manipulation, it can be convenient
to collect several rules in one variable:

displayNicely={ Csc[z_] -> 1/sin[z],Sec[z_]->1/cos[z]}

Then you can just append /.displayNicely to any calculation to obtain
this effect!

David Bailey

http://www.dbaileyconsultancy.co.uk

```

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