# Proof Theory for all real numbers

1. Mar 24, 2008

### cannibal

[SOLVED] Proof Theory for all real numbers

1. The problem statement, all variables and given/known data

If a and b are real numbers, we define max {a, b} to be the maximum of a and b or the common value if they are equal.

Prove that for all real numbers d, d1, d2, x, If d = max {d1, d2} and x ≥ d, then x ≥ d1 and x ≥ d2.

2. Relevant equations

3. The attempt at a solution

I do not know how to even start this problem, i have a small feeling that this exercise has something in relation with the "Logic and propositional calculus topic" but i have not find out were to link it. Any hint or good start will be appreciated.

Thanks

2. Mar 24, 2008

### HallsofIvy

Staff Emeritus
Why in the world is this in "Engineering, Computer Science, and Technology"? Looks like a straightforward math problem to me. First, we have, from the definition, $max(d_1,d_2)\ge d1$ and $max(d_1,d_2)\ge d2$. It follows immediately that if $x\ge max(d1,d2)$ then $x\ge d1$ and $x\ge d2$.

3. Mar 25, 2008

### cannibal

Thank you very much "HallsofIvy" i put it here since its a "Computer Science Class" at my college, I am currently studying "Computer Engineer" and i have to take this class.

Thanks!