rtoy
commented
4 months ago Imported from SourceForge on 2024-07-06 17:15:09 Created by fabriziocaruso on 2018-11-27 07:43:46 Original: https://sourceforge.net/p/maxima/bugs/3424/#0979
Most of the problems related to sign of polynomial expressions can be solved with the SARAG package that is included in Maxima. I am going to work on a better integration with Maxima's top-level commands.
Imported from SourceForge on 2024-07-06 17:15:08 Created by gutoo on 2018-04-19 12:25:20 Original: https://sourceforge.net/p/maxima/bugs/3424
I would like to calculate a sign of -2a1^2a2^2+2*a2^2+a1^2-1 when a2^2>=1/2, 1>=a2^2, 1>=a1^2. By the way, according to a variety of expressions of the same polynomial expression. sign calculate a sign correctly or incorrectly.
(%i87) facts(); (%o87) [a2^2>=1/2,1>=a2^2,1>=a1^2] (%i82) p1:(1-a1^2)a2^2-(1-a1^2)(1-a2^2); (p1)(1-a1^2)a2^2-(1-a1^2)(1-a2^2) (%i88) sign(p1); (%o88) pnz -> Wrong answer. It must be pz. (%i89) expand(p1); (%o89) -2a1^2a2^2+2a2^2+a1^2-1 (%i90) sign(expand(p1)); (%o90) pnz -> Wrong answer. It must be pz. (%i91) p2:(1-a1^2)(2a2^2-1); (p2)(1-a1^2)(2a2^2-1) -> The same expression of -2a1^2a2^2+2a2^2+a1^2-1. (%i92) sign(p2); (%o92) pz -> Right answer. (%i93) sign(expand(p2)); (%o93) pnz -> Wrong answer. It must be pz.