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Topic: Proving trigonometric identities
Replies: 32   Last Post: Jan 27, 2009 1:59 AM

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 Guest
Re: Proving trigonometric identities
Posted: Jan 20, 2009 3:41 AM

On Jan 20, 7:22 pm, Angus Rodgers <twir...@bigfoot.com> wrote:
> On Tue, 20 Jan 2009 08:19:58 +0000, I groggily wrote:
> >[...] So, the identity you have to prove is
> >equivalent to the one you have just written out - which follows
> >simply from the given algebraic identity [...]

>
> ... in conjunction, of course, with the known trigonometric
> identity:
>
>   cos(x)^2 + sin(x)^2 = 1
>
> --
> Angus Rodgers

Are you implying that (1+sinx)(1-sinx) = 1 - (sinx)^2 = 1 - (sin^2)x =
1 - sin(x)^2
?

My booklet writes square relations (sin^2)x, you seem to write sin(x)
^2 and I've always thought that sinx * sinx = (sinx)^2 which was not
equal to (sin^2)x. Which means I MUST have been wrong because = 1 -
(sinx)^2 WOULD result in no further steps possible. But as I've
clearly seen, it gets re-arranged (with some correct stuff on the left
hand side of the equals sign) to be one of the trigonometric
identities and therefore my original problem is proven!... :|

Date Subject Author
1/20/09 Albert
1/20/09 Angus Rodgers
1/20/09 Albert
1/20/09 Angus Rodgers
1/20/09 Albert
1/20/09 Angus Rodgers
1/20/09 Angus Rodgers
1/20/09 Guest
1/20/09 Angus Rodgers
1/20/09 Albert
1/20/09 Angus Rodgers
1/20/09 matt271829-news@yahoo.co.uk
1/21/09 Albert
1/21/09 matt271829-news@yahoo.co.uk
1/23/09 Albert
1/23/09 Angus Rodgers
1/23/09 Angus Rodgers
1/23/09 Passerby
1/23/09 Dave Dodson
1/24/09 Albert
1/24/09 Angus Rodgers
1/24/09 Albert
1/26/09 Albert
1/26/09 Driveby
1/26/09 Albert
1/26/09 A N Niel
1/27/09 Albert