simple inequality check fails - why?

Hi,

I have the simple inequality check for testing purposes in MuPad:

assume(0<x<1)
assumeAlso(0<y<1)
assumeAlso(A>0)
is(1/(1-x) >=1/(1-x*y))    
is(A/(1-x) >=A/(1-x*y))

The first check correctly evaluates to TRUE, but the second returns UNKNOWN, however it is obviously true. Am I doing something wrong, or I have reached the limitation of the tool?

Answer 1

[Tom]

You have to split up the comparisons: e.g.:

x > 0 & x < 1

[L. C.]

Thanks. I tried and nothing has changed. Other ideas? I also tried to introduce an upper bound on A as well to avoid possible mess with infinity, but the result is just the same.

Answer 2

[Radu Trimbitas]

Your code works works correctly in MATLAB 2014a.

Answer 3

[timo]

For me evaluates to:

TRUE TRUE

in mupad for Symbolic Math Toolbox Version 6.1 (R2014b)