Two exercises to which I have (really) no clue.

Explain how

**Common Notions 1** and

**4** may be interpreted as the

transitive and

reflexive properties.

Note that the natural way to write **Common Notion 1** symbolically is slightly different from the statement of transitivity above.
Show that the

symmetric property follows from

**Common Notions 1 **and

**4**.

The book goes on to say:

"Hilbert took advantage of **Common Notions 1 **and **4** in his rectification of Euclid's axiom system. He *defined* equality of length by postulating a transitive and reflexive relation on line segments, and stated transitivity in the style of Euclid, so that the symmetric property was a consequence."
Could someone outline what he'd done (or point to other source)?