# Proof Theory for all real numbers

[SOLVED] Proof Theory for all real numbers

1. Homework Statement

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. Homework 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

## Answers and Replies

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HallsofIvy
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 $x\ge d2$.