Lesson 29.

NOTE 1: Be sure to read Homework Format and Homework Writing Policy BEFORE writing up your solutions to be turned in.

Due Friday, October 31 (Happy Halloween!)

Sect. 3.7:
For any set  D  and any number  a,  let  [D < a]  denote the set of all elements of  D  which are less than  a,  and define  [D > a]  analogously.

  1. Prove that if  a  is a limit point of either  [D < a]  or  [D > a],  then  a  is a limit point of  D.

Suppose that  a  is a limit point of both  [D < a]  and  [D > a].  Let  f  be a real-valued function on  D.  Denote by  f<a  the restriction of  f  to  [D < a],  and define  f>a  analogously.

  1. Explain why all the relevant domains  ( [D < a],  etc.) are nonempty.
  2. Let  L  be a real number. Show that if  f  has the limit  L  at  a,  then both  f<a  and  f>a  have the limit  L  at  a.
    (Note:  “f  has the limit  L  at  a”  means the same as  “the limit as  x  approaches  a  of  f(x)  is L )
  3. State and prove the converse of the preceding statement.

NOTE: As stated on the Course Home Page, all due dates are tentative. Assignments, or parts of assignments, may be postponed to a later date.


Last modified Oct 23, 2008

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