Minhtri's profile - activity

I write the following piece of code:

x = var('x')
assume(x,'real')
y = var('y')
assume(y,'real')
z = var('z')
assume(z,'real')

expr = abs(x-y)+abs(y-z) >= abs(x-z)

Then I run it:

sage: bool(expr)
False

The expr is the triangle inequality, which is True for any real x, y, z. How come SageMath returns False? What should I do to make SageMath work in this case? Thanks much!

I wrote the following code:

x = var('x')
assume(x,'real')
y = var('y')
assume(y,'real')
z = var('z')
assume(z,'real')

expr = abs(x-y)+abs(y-z) >= abs(x-z)

Then I run it:

sage: bool(expr)
False

The expression is obviously mathematically correct. How come Sage returns "False"?