I want to invert a matrix that contains some variables, so I thought I should give some assumptions to Mathematica to speed up the process.

How do I assume that $s0,...,s8$ are positive constants between 1 and 10 in the following?

Inverse[{{s0, s1, s2}, {s3, s4, s5}, {s6, s7, s8}}]
  • 1
    $\begingroup$ Inverse does not take Assumptions as an option, and I rather suspect all functions it uses for handling the symbolic case (e.g. Together) do not either. So the Assuming/Assumptions framework is not going to be relevant. Moreover I do not see any way in which it would help, for the particulars described above. $\endgroup$ – Daniel Lichtblau Mar 16 '15 at 15:28

You can do it as

{s0 > 0, s1 > 0, s2 > 0, s3 > 0, s4 > 0, s5 > 0, s6 > 0, s7 > 0, s8 > 0},
Inverse[{{s0, s1, s2}, {s3, s4, s5}, {s6, s7, s8}}]] 

For instance, If you get $s0=-1$, then you will get the error

$Assumptions::fas: Warning: one or more assumptions evaluated to False..

Also you can determine the condition

s0 > 0 && s0 < 11

for all your numbers.

Good Luck.

  • $\begingroup$ These Assumptions does not change anything regarding to speed and to the representation of the result $\endgroup$ – Rom38 Mar 16 '15 at 20:32

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