# Non-polynomial inequality with multi variables [closed]

**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!**

### Closed for the following reason
**duplicate question** by
*John Palmieri *

close date 2019-12-20 16:29:56.718769

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