Re: PolynomialQ (wrong) behavior ?
- To: mathgroup at smc.vnet.net
- Subject: [mg19280] Re: [mg19199] PolynomialQ (wrong) behavior ?
- From: "Tomas Garza" <tgarza at mail.internet.com.mx>
- Date: Thu, 12 Aug 1999 01:24:30 -0400
- Sender: owner-wri-mathgroup at wolfram.com
Drago Ganic [drago.ganic at in2.hr] wrote: > f = 2x +1 > > PolynomialQ [ f, x ] > True > > That's OK. But why the following > > PolynomialQ [ f, y ] > True > > PolynomialQ [ f, Sin[x] ] > True I guess you're trying to substitute Sin[x} in your f so as to obtain 2 Sin[x] + 1 which is certainly not a polynomial in x. But what you are asking is whether it is a polynomial in Sin[x], so that the test gives True, as it should. I think you can avoid the problem by being more precise, for example: In[1]:= f[x_] := 2 x + 1 In[2]:= PolynomialQ[f[x], x] Out[2]= True In[3]:= PolynomialQ[f[Sin[x]], x] Out[3]= False But, of course: In[4]:= PolynomialQ[f[x], Sin[x]] Out[4]= True which roughly corresponds to what you had in your question. Bear in mind that Sin is a symbol. Tomas Garza Mexico City