Re: Trigonometric simplification

• To: mathgroup at smc.vnet.net
• Subject: [mg68904] Re: Trigonometric simplification
• From: Paul Abbott <paul at physics.uwa.edu.au>
• Date: Tue, 22 Aug 2006 05:20:55 -0400 (EDT)
• Organization: The University of Western Australia
• References: <ecbnnc\$r29\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```In article <ecbnnc\$r29\$1 at smc.vnet.net>, carlos at colorado.edu wrote:

> As an intermediate result of some calculations I have
> the expression
>
>    r=Tan[a]^2/(Sec[a]^2)^(3/2)
>
> where a is real. How can I coerce Mathematica into
> simplifying that to
>
>    r=Cos[a]*Sin[a]^2

It doesn't simplify because it is not true in general for a real.
However,

Simplify[Tan[a]^2/(Sec[a]^2)^(3/2), -(Pi/2) < a < Pi/2]

Cos[a] Sin[a]^2

and

Simplify[Tan[a]^2/(Sec[a]^2)^(3/2), Pi/2 < a < 3 Pi/2]

-(Cos[a] Sin[a]^2)

Cheers,
Paul

_______________________________________________________________________
Paul Abbott                                      Phone:  61 8 6488 2734
School of Physics, M013                            Fax: +61 8 6488 1014
The University of Western Australia         (CRICOS Provider No 00126G)
AUSTRALIA                               http://physics.uwa.edu.au/~paul

```

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