On Jan 20, 6:40 pm, Angus Rodgers <twir...@bigfoot.com> wrote: > On Mon, 19 Jan 2009 23:31:43 -0800 (PST), Albert > > <albert.xtheunkno...@gmail.com> wrote: > >On Jan 20, 6:25 pm, Angus Rodgers <twir...@bigfoot.com> wrote: > >> Are you familiar with the algebraic identity (a + b)(a - b) = a^2 - b^2? > > >Yes I am - are you implying the following steps: > >(cosx)^2 = (1 + sinx)(1 - sinx) > >..``..``.= 1 - (sinx)^2 > >? > > Yes, I was, but you hardly need to know what I was thinking, > because the result is clear now, isn't it?
I don't think that it's a proof though. Please enlighten me.