MathGroup Archive 2009

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Wrong Simplify[] Answer for Simplify[Cos[x]^4-Sin[x]^4]?


Because

(Cos[x]^4 - Sin[x]^4)  =  (Cos[x]^2 - Sin[x]^2) (Cos[x]^2 + Sin[x]^2)

and

Cos[x]^2 + Sin[x]^2 = 1

--David

On Oct 30, 3:20 am, Lawrence Teo <lawrence... 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.



  • Prev by Date: Re: FTP directly from Mathematica
  • Next by Date: Re: Wrong Simplify[] Answer for Simplify[Cos[x]^4-Sin[x]^4]?
  • Previous by thread: Re: Wrong Simplify[] Answer for Simplify[Cos[x]^4-Sin[x]^4]?
  • Next by thread: Re: Wrong Simplify[] Answer for Simplify[Cos[x]^4-Sin[x]^4]?