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Re: how to test if 2 expressions are the same? Mathematica 5.0
*To*: mathgroup at smc.vnet.net
*Subject*: [mg46096] Re: how to test if 2 expressions are the same? Mathematica 5.0
*From*: bobhanlon at aol.com (Bob Hanlon)
*Date*: Fri, 6 Feb 2004 04:15:19 -0500 (EST)
*References*: <bvt135$oj5$1@smc.vnet.net>
*Sender*: owner-wri-mathgroup at wolfram.com
Use Equal (==); however, you will also frequently have to use Simplify or
FullSimplify.
1-Sin[x]^2 == Cos[x]^2
1 - Sin[x]^2 == Cos[x]^2
%//Simplify
True
You may also have to state Assumptions that would make the equality True
a*Log[x] == Log[x^a] // Simplify
a*Log[x] == Log[x^a]
Simplify[%, {Element[{a,x}, Reals], x>0}]
True
Sometimes there are shortcuts using PowerExpand; however, you need to be sure
that the implied assumptions hold.
a*Log[x] == Log[x^a] // PowerExpand
True
Bob Hanlon
In article <bvt135$oj5$1 at smc.vnet.net>, nma124 at hotmail.com (steve_H) wrote:
<< many times, I want to find if there is a way to obtain one expression
from another by tranformation.
for example, we know that 1-sin^2(x) = cos^2(x), and a*log(x)=log(x^a),
etc.., but sometimes this does not seem to work using SameQ:
SameQ[a Log[x], Log[x^a] ]
False
I tried MatchQ and that also gives False.
what is the right way to do these things in Mathematica? I checked the on-line
help,
and can't seem to see the right command for this.
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