Albert
Posts:
282
Registered:
12/9/07


Re: Proving trigonometric identities
Posted:
Jan 20, 2009 3:11 AM


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.

