Re: Wrong Simplify[] Answer for Simplify[Cos[x]^4-Sin[x]^4]?
- To: mathgroup at smc.vnet.net
- Subject: [mg104440] Re: [mg104400] Wrong Simplify[] Answer for Simplify[Cos[x]^4-Sin[x]^4]?
- From: Leonid Shifrin <lshifr at gmail.com>
- Date: Sat, 31 Oct 2009 01:55:08 -0500 (EST)
- References: <200910300719.CAA27787@smc.vnet.net>
Hi Lawrence, Well, look: Cos[x]^4-Sin[x]^4] == (Cos[x]^2-Sin[x]^2)*(Cos[x]^2+Sin[x]^2) But Cos[x]^2+Sin[x]^2 == 1 Regards, Leonid On Fri, Oct 30, 2009 at 10:19 AM, 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. > >
- References:
- Wrong Simplify[] Answer for Simplify[Cos[x]^4-Sin[x]^4]?
- From: Lawrence Teo <lawrenceteo@yahoo.com>
- Wrong Simplify[] Answer for Simplify[Cos[x]^4-Sin[x]^4]?