READING: I §3 11
Back to reading:
I §3 10
begin quote ita"
CHAPTER I [:] Notions from Set Theory [...] §3. FUNCTIONS. "end quote
These pages assume that the reader has the book and is reading along. topic index contents
Please read these notes from the beginning to here and then paragraph 9 of §3.
THE INVERSE IMAGE OF A SET UNDER A FUNCTION
If f : X → Y is a function and Y Y, then the subset of X given by
And now, without confusion (among those who have mastered the concepts I suppose):
If f : X → Y happens to be one-one onto we have another use for the symbol f , namely the inverse function f : Y → X. These two uses of f must be carefully distinguished, though confusion rarely arises. If f : X → Y is one-one onto then the two uses of f are related by
To avoid confusion, just look again at the topic of this page. If what is inside the parentheses is a set, then we have the inverse image of a set.