Mathematica简化测试！Why？

zeroieme

1. Simplify[{Abs[(-Subscript[m, 2] Subscript[n, 1]+Subscript[m, 1] Subscript[n, 2])],Abs[(-Subscript[m, 3] Subscript[n, 2]+Subscript[m, 2] Subscript[n, 3])],Abs[(-Subscript[m, 3] Subscript[n, 1]+Subscript[m, 1] Subscript[n, 3])]},Subscript[m, 1]>0&&Subscript[n, 1]>0&&Subscript[m, 2]>0&&Subscript[n, 2]>0&&Subscript[m, 3]>0&&Subscript[n, 3]>0&&Subscript[m, 3]/Subscript[n, 3]>Subscript[m, 2]/Subscript[n, 2]>Subscript[m, 1]/Subscript[n, 1]]
   
2. 
   
3. FullSimplify[{Abs[(-Subscript[m, 2] Subscript[n, 1]+Subscript[m, 1] Subscript[n, 2])],Abs[(-Subscript[m, 3] Subscript[n, 2]+Subscript[m, 2] Subscript[n, 3])],Abs[(-Subscript[m, 3] Subscript[n, 1]+Subscript[m, 1] Subscript[n, 3])]},Subscript[m, 1]>0&&Subscript[n, 1]>0&&Subscript[m, 2]>0&&Subscript[n, 2]>0&&Subscript[m, 3]>0&&Subscript[n, 3]>0&&Subscript[m, 3]/Subscript[n, 3]>Subscript[m, 2]/Subscript[n, 2]&&Subscript[m, 2]/Subscript[n, 2]>Subscript[m, 1]/Subscript[n, 1]&&Subscript[m, 3]/Subscript[n, 3]>Subscript[m, 1]/Subscript[n, 1]]

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chyanog

How

1. assum=m1>0&&n1>0&&m2>0&&n2>0&&m3>0&&n3>0&&m3/n3>m2/n2>m1/n1;
   
2. 
   
3. expr={Abs[-m2 n1+m1 n2],Abs[-m3 n2+m2 n3],Abs[-m3 n1+m1 n3]};
   
4. 
   
5. PiecewiseExpand[expr,Reals,Method->{"ConditionSimplifier" -> (Reduce[#&&assum]&)}]
   
6. 
   
7. FullSimplify[expr,TransformationFunctions->{Automatic,PiecewiseExpand[#,Reals,Method->{"ConditionSimplifier" -> (Reduce[#&&assum]&)}]&}]

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zeroieme

1. PiecewiseExpand[{Abs[-m2 n1 + m1 n2], Abs[-m3 n2 + m2 n3],
   
2.   Abs[-m3 n1 + m1 n3]}, Reals,
   
3. Method -> {"ConditionSimplifier" -> (Reduce[# && n1 > 0 && n2 > 0 &&
   
4.         n3 > 0 && m3/n3 > m2/n2 > m1/n1 > 0] &)}]

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