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MathGroup Archive 2006

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Re: Trigonometric simplification

  • To: mathgroup at smc.vnet.net
  • Subject: [mg68890] Re: Trigonometric simplification
  • From: "Dana DeLouis" <dana.del at gmail.com>
  • Date: Tue, 22 Aug 2006 05:20:29 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

>   r=Tan[a]^2/(Sec[a]^2)^(3/2)
>     simplifying that to
>   r=Cos[a]*Sin[a]^2

r = Tan[a]^2/(Sec[a]^2)^(3/2); 

Hi.  Just one of a few ways. With a Sqrt on Sec[a], try to find values of 'a
where Sec[a] is positive.
Since I've forgotten what they are...

Plot[Sec[a], {a, -Pi, Pi}, 
   Ticks -> {Range[-Pi, Pi, Pi/4], Automatic}]; 

Therefore:
Assuming[{-Pi/2 < a < Pi/2}, Simplify[r]]

Cos[a]*Sin[a]^2

-- 
HTH.  :>)
Dana DeLouis
Windows XP, Mathematica 5.2


<carlos at colorado.edu> wrote in message news:ecbnnc$r29$1 at smc.vnet.net...
> 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
> 
> Both Simplify and FullSimplify with assumptions on a
> fail to get the simpler form.
>


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