unevaluated boolean and conditional expressions (take 1)

(OK, I don't see any damage compared to current situation :)

As for more elaborate deductions, consider

assume(x>=0 and y>=0)
is (x^2+y^2>0)    -->     is (not (x=0 and y=0))

is(x*y>=0) --> true

assume(z^2<1)

is ( -1<z and z<1)   --> true
.........

There is a literature on "cylindrical algebraic decomposition"
for solving such questions.
RJF