Re: Wrong Simplify[] Answer for
- To: mathgroup at smc.vnet.net
- Subject: [mg104415] Re: [mg104400] Wrong Simplify[] Answer for
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Sat, 31 Oct 2009 01:50:07 -0500 (EST)
- Reply-to: hanlonr at cox.net
The only difference is numerical noise, i.e., close to the specifed precision. For example, specifying a precision of 200, the difference is less than 10^-198
Chop[Table[(Cos[x]^2 - Sin[x]^2) -
(Cos[x]^4 - Sin[x]^4),
{x, 0, 7, .001`200}], 10^-198] // Union
{0}
Bob Hanlon
---- Lawrence Teo <lawrenceteo at yahoo.com> wrote:
=============
We know that Simplify[Cos[x]^2-Sin[x]^2] -> Cos[2 x]
But why Simplify[Cos[x]^4-Sin[x]^4] -> Cos[2 x] too?
Doing subtraction between the two expressions will give small delta.
This is enough to prove that the two expression shouldn't be the same.
Can anyone give me any insight? Thanks.