when elements can be listed, a set is said to be countable
[a,b) = {x is an element of R : a </= x < b
S and T are disjoint if the intersect of S and T is the empty set
a subsequence of {Xk} is an infinite subset of the elements, in the same order
a set is closed if and only if its complement is open (a closed set contains its boundary)
a subset of R^n is compact if and only if it is closed and bounded
Bolzano-Weierstrass theorem: if S is a compact subset of R^n, then every sequence of points in S has a subsequence that converges to a point in S
[a,b] is closed, bounded and convex
(a,b) is open, bounded and convex
(a,b] is neither open nor closed but is bounded and convex
if S is bounded above, then there is an upper bound b* such that if b is an upper bound for S, b*<=b and is called the supremum, or the least upper bound
inf(S) is the infimum or the greatest lower bound
f: S -> T
S is the domain of the function, and T is the range
monotonic means increasing or decreasing
any strictly monotonic function has an inverse
Weierstrass theorem - a continuous function f: S -> R where S is a compact subset of R, attains a maxmimum and minimum value on S
when a Taylor series converges, it is the Taylor expansion of f about a