06-240/Classnotes For Tuesday, September 12

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• PDF notes by User:Harbansb: September 12 Notes.
• If I have made an error in my notes, or you would like the editable OpenOffice file, feel free to e-mail me at harbansb@msn.com.
• September 12 Notes for re-uploading, please email at jeff.matskin@utoronto.ca
• Below are a couple of lemmata critical to the derivation we did in class - the Professor left this little work to the students:
  • 06-240: Edit1.jpg
  • 06-240: Edit2.jpg

Notes

The Real Numbers

The Real Numbers are a set (denoted by $\mathbb {R}$) along with two binary operations: + (plus) and · (times) and two special elements: 0 (zero) and 1 (one), such that the following laws hold true:

$\mathbb {R} 1:\forall a,b\in \mathbb {R} \quad a\cdot b=b\cdot a\quad {\mbox{and}}\quad a+b=b+a$ (The Commutative Laws)