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Re: Trigonometric simplification


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

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Paul Abbott                                      Phone:  61 8 6488 2734
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The University of Western Australia         (CRICOS Provider No 00126G)    
AUSTRALIA                               http://physics.uwa.edu.au/~paul


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