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#2516 Maxima fails to determine equivalence of radicals, spurious false value

None
open
nobody
Lisp Core (472)
5
2012-12-30
2012-12-12
fredOnMaxima
No

a:sqrt((2-sqrt(2))^2+2)/2;
b:sqrt(2-sqrt(2));
bfloat(a);
7.653668647301796b-1
bfloat(b);
7.653668647301796b-1
is(equal(a,b));
false
and normally it's true

Discussion

  • Raymond Toy
    Raymond Toy
    2012-12-15

    I think this is fairly consistent with how maxima behaves. a-b doesn't instantly return 0; you have to apply some transformations (radcan) to get 0.

    Marking as pending.

     
  • Raymond Toy
    Raymond Toy
    2012-12-15

    • status: open --> pending
     
  • Robert Dodier
    Robert Dodier
    2012-12-30

    • labels: --> Lisp Core
    • summary: normally it's equal (about sqrt(..)) --> Maxima fails to determine equivalence of radicals, spurious false value
    • status: pending --> open
     
  • Robert Dodier
    Robert Dodier
    2012-12-30

    Well, this is a real bug -- if Maxima can't determine the equivalence of the two radical expressions, it should return unknown instead of false.

    (It is a lesser bug that it can't determine the equivalence of the two expressions. But the main problem is the spurious false value.)