Re: Simplifying trigonometric functions
- To: mathgroup at smc.vnet.net
- Subject: [mg94729] Re: Simplifying trigonometric functions
- From: David Bailey <dave at removedbailey.co.uk>
- Date: Mon, 22 Dec 2008 05:15:13 -0500 (EST)
- References: <gig3ph$2k4$1@smc.vnet.net>
Tang wrote:
> Hi,
> I'm new to Mathematica.
> How can I define a rule to reduce the following expression
> from
> Cos[x] Cos[y]^2 + Sin[y]^2
>
> to operate only on expressions involving y to
>
> Cos[x](1+Cos[2y])/2 + (1-Cos[2y])/2
>
> Thanks for the help!
>
Note that if you just want to check an identity, FullSimplify will often
(but not always - it only has finite power) do the trick:
(Cos[x] Cos[y]^2 + Sin[y]^2 ==
Cos[x] (1 + Cos[2 y])/2 + (1 - Cos[2 y])/2
) // FullSimplify
True
David Bailey
http://www.dbaileyconsultancy.co.uk