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MathGroup Archive 1997

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Re: PowerExpand, Apart, Simplify

  • To: mathgroup at smc.vnet.net
  • Subject: [mg5670] Re: [mg5654] PowerExpand, Apart, Simplify
  • From: rhall2 at umbc.edu (hall robert)
  • Date: Tue, 7 Jan 1997 11:22:46 -0500
  • Organization: University of Maryland, Baltimore County
  • Sender: owner-wri-mathgroup at wolfram.com

In article <5ap4kr$kv2 at dragonfly.wolfram.com>,
Allan Hayes  <hay at haystack.demon.co.uk> wrote:
>"Lidar (Hamburger) dani" <dani at fh.huji.ac.il>
> [mg5654] PowerExpand, Apart, Simplify
> writes
>
>> ...I have not been able to find any way to make Mathematica
>>tell me that the following expression equals 1 (using the built-in  
>>functions,that is):
>>
>>Sqrt[3 x^(4j)+x^(12j)]/(x^(2j)Sqrt[3 + x^(8j)])
>>(x,j real and positive)
>
>
>Dani:
>
>Factor//@Sqrt[3 x^(4j)+x^(12j)]/(x^(2j)Sqrt[3 + x^(8j)])
>	      4 j       8 j
>	Sqrt[x    (3 + x   )]
>	---------------------
>	  2 j           8 j
>	 x    Sqrt[3 + x   ]
>
>PowerExpand[%]
>	1
>	
>?//@
>	MapAll[f, expr] or f //@ expr applies f to every 	
>	subexpression in expr.

Using 2.2.2, MapAll isn't necessary.

In[6]:=
   Sqrt[3 x^(4j)+x^(12j)]/(x^(2j)Sqrt[3 + x^(8j)])
Out[6]=
           4 j    12 j
   Sqrt[3 x    + x    ]
   --------------------
    2 j           8 j
   x    Sqrt[3 + x   ]

And PowerExpand[] doesn't work.

In[7]:=
   PowerExpand[%]
Out[7]=
           4 j    12 j
   Sqrt[3 x    + x    ]
   --------------------
    2 j           8 j
   x    Sqrt[3 + x   ]

-- 
Bob Hall            | "Know thyself? Absurd direction!
rhall2 at gl.umbc.edu  |  Bubbles bear no introspection."  -Khushhal Khan Khatak


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