L5_A
2.4 Accumulation points (補充)
L5_B
2.5 Closure of a set(cont.)
2.5 Closure of a set(cont.)
(1)definition
(2)Thm of the closure of a set A.
(3)closure & ∩、∪,?
L5_C
2.5 Closure of a set(cont.)
2.5 Closure of a set(cont.)
(1) cl(A) is the set of all points in M whose every
neighborhood meets A
(2)或是cl(A)={x∈M | every neighborhood of x meets A}.
(2)或是cl(A)={x∈M | every neighborhood of x meets A}.
L5_D
2.6 Boundary of a set
(1)definition of boundary
(2)property of bd(A)
(3)example:boundary of a ball