Mistake in applying a rule
- To: mathgroup at smc.vnet.net
- Subject: [mg80658] Mistake in applying a rule
- From: Steven Siew <siewsk at bp.com>
- Date: Tue, 28 Aug 2007 02:12:34 -0400 (EDT)
Hi, I'm trying to show that Integrate[Cos[x-a]] is Sin[x-a] + C I manage to get Simplify @ Integrate[Cos[x-a]] to give -Sin[a-x] This is fine because Sin[-x] is equal to -Sin[x] But when I apply the rule Times[-1,Sin[Plus[g_,Times[-1,h_]]]] -> Sin[h-g] it fails. Here is the complete transcript. Mathematica 5.2 for Students: Microsoft Windows Version Copyright 1988-2005 Wolfram Research, Inc. In[1]:= Out[1]= {stdout} In[2]:= (* Write your mathematica code below *) In[3]:= Simplify @ Integrate[Cos[x-a],x] Out[3]= -Sin[a - x] In[4]:= FullForm[%] Out[4]//FullForm= Times[-1, Sin[Plus[a, Times[-1, x]]]] In[5]:= % /. Times[-1,Sin[Plus[g_,Times[-1,h_]]]] -> Sin[h-g] Out[5]= -Sin[a - x] In[6]:= (* End of mathematica code *) In[7]:= Quit[];