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Useful links

Office hours:

  • Mondays 9:00-10:00
  • Wednesdays 14:00-16:00

Email

GSI:

Rahul Dalal
  • M 10:30-12:30
  • TTh 17:30-19:30
  • WF 11:00-13:00

Exams

  1. Suppose that $(S, \preceq)$ is an ordered set, that $E \subseteq S$, and that $t$ is a lower bound for $E$. Then for any $x \prec t$, $x$ is a lower bound for $E$.
    1. True.
    2. True, but only with the additional assumption that $t = \inf E$.
    3. False.
  2. Suppose that $(S, \preceq)$ is an ordered set, and $E \subseteq S$ is bounded above. Then $E$ has infinitely many distinct upper bounds...
    1. ...with no further assumptions.
    2. ...provided that $E$ does not have a maximum element.
    3. ...provided that $S$ does not have a maximum element.
    4. ...if $S$ has the least upper bound property.
  3. Suppose $(S, \square)$ is an ordered set, and $E \subseteq S$. We say $E$ is bounded above if...
    1. ...for every $t \in E$ there is some $s \in S$ with $t \square s$.
    2. ...$\sup E$ exists.
    3. ...there is some $s \in S$ so that for every $t \in E$, $t \square s$.
    4. ...whenever $s \in S$ and $t \in E$, we have $t \square s$.