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[1]:= > Unprotect[Cos, Sin]; > Format[Cos[x_] := "c" <> ToString[x]]; > Format[Sin[x_] := "s" <> ToString[x]]; > > In[4]:= > Expand[(Cos[x] + Sin[t])^3] > Out[4]= "cx"^3 + 3*"cx"^2*"st" + 3*"cx"*"st"^2 + "st"^3 > > In[5]:= TrigExpand[% /. t -> x] > Out[5]= 1 + 2*"cx"*"sx" > > Peter > Something went terribly wrong: The above Mathematica-lines should read In[1]:= Unprotect[Cos,Sin]; Format[Cos[x_]]:="c"<>ToString[x]; Format[Sin[x_]]:="s"<>ToString[x]; Expand[(Cos[x]+Sin[t])^2] Out[4]= "cx"^2 + 2*"cx"*"st" + "st"^2 In/Out[5] are correct. Peter