Re: Surprising FullSimplify result
- To: mathgroup at smc.vnet.net
- Subject: [mg111510] Re: Surprising FullSimplify result
- From: "David Park" <djmpark at comcast.net>
- Date: Tue, 3 Aug 2010 06:42:48 -0400 (EDT)
Two techniques that are useful for manipulating or simplifying expressions are: 1) Protect certain subexpressions against participating in simplifications by using a Hold or HoldForm. 2) Operate only on a selected subset of level parts in an expression. The following uses the first technique: Cos[theta]^2 + Sin[theta]^2 + L^2 Cos[theta]^2; MapAt[Hold, %, 2]; % // Simplify // ReleaseHold 1 + L^2 Cos[theta]^2 The second technique can be implemented using the MapLevelParts or MapLevelPatterns routines in the Presentations Manipulation subsection. Needs["Presentations`Master`"] Cos[theta]^2 + Sin[theta]^2 + L^2 Cos[theta]^2; % // MapLevelParts[Simplify, {{1, 3}}] 1 + L^2 Cos[theta]^2 Or using patterns and TrigExpand instead: Cos[theta]^2 + Sin[theta]^2 + L^2 Cos[theta]^2; % // MapLevelPatterns[TrigExpand, {{(Sin | Cos)[_]^2}}] 1 + L^2 Cos[theta]^2 David Park djmpark at comcast.net http://home.comcast.net/~djmpark/ From: Sam Takoy [mailto:sam.takoy at yahoo.com] Here's what I am getting Cos[theta]^2 + Sin[theta]^2 // FullSimplify Out[540]= 1 Cos[theta]^2 + Sin[theta]^2 + L^2 Cos[theta]^2 // FullSimplify Out[541]= 1/2 (2 + L^2 + L^2 Cos[2 theta]) I'm really surprised that the answer in the latter case is not 1+ L^2 Cos[theta]^2 Is there an explanation? Thanks, Sam