Inconsistent Outputs Using MuPAD "assume" Command

Why does the following MuPAD code generate the "UNKNOWN" outputs shown? I should be getting "FALSE" outputs instead.

delete x: delete a: delete b: delete c:
assume(a>0); assumeAlso(0<c<1): assumeAlso((a*(1-c))<x<(a*(1+c))):
is((a*(1-c))>0);
is(x>(a*(1-c)));
delete x: delete a: delete b: delete c:
assume(a>0); assumeAlso(0<c<1): assumeAlso((a*(1-c))<x<(a*(1+c))):
is((a*(1-c))<0);
is(x<(a*(1-c)));

TRUE
TRUE
UNKNOWN
UNKNOWN

Answer 1

[Walter Roberson]

if is((a*(1-c))>0) is TRUE then why would is((a*(1-c))<0) be TRUE ? The first expression is the same but the comparison is opposite so they are disjunctions. If one is TRUE then the other should be FALSE.

[Amr]

Of course, it should give me FALSE. My mistake. I corrected the question. Still though, why is MuPAD giving me UNKNOWN?

[Walter Roberson]

I don't know at the moment. Try reversing the order of the subsections. If it is the first subsection that works, then you need to use a "syms clear" not just a "clear"; see http://www.mathworks.com/help/symbolic/clear-assumptions-and-reset-the-symbolic-engine.html