Help with Real analysis proof about limit laws and functions

Click For Summary
SUMMARY

The discussion centers on proving that if the limit of a function f as x approaches p is L (where L > 0), then f(x) must be greater than L/2 in the vicinity of p. The proof utilizes the epsilon-delta definition of limits, specifically setting ε = |L|/2 and demonstrating that for any δ > 0, the condition |f(x) - L| > |L|/2 holds true. This confirms that f(x) exceeds L/2 near the point p, validating the limit laws in real analysis.

PREREQUISITES
  • Understanding of limit definitions in real analysis
  • Familiarity with epsilon-delta proofs
  • Knowledge of the properties of continuous functions
  • Basic concepts of inequalities in mathematical proofs
NEXT STEPS
  • Study the epsilon-delta definition of limits in more depth
  • Explore proofs involving continuity and limits in real analysis
  • Learn about the implications of limit laws in calculus
  • Review examples of limit proofs in real analysis textbooks
USEFUL FOR

Students of real analysis, mathematics educators, and anyone looking to strengthen their understanding of limit proofs and epsilon-delta arguments.

kbrono
Messages
16
Reaction score
0

Homework Statement


Let f be a function let p /in R. Assume limx->p=L and L>0. Prove f(x)>L/2


The Attempt at a Solution



Let f be a function let p /in R. Given that limx->pf(x)=L and L>0. Since L\neq0 Let \epsilon= |L|/2. Then given any \delta>0 and let p=0 we have |f(x)-L| = |0-L| = |L| > |L|/2=\epsilon. Thus f(x) > |L|/2 near p.
 
Physics news on Phys.org
Yes, this seems to be correct!
 
Thank you!
 

Similar threads

Replies
4
Views
2K
Replies
4
Views
2K
  • · Replies 21 ·
Replies
21
Views
1K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 13 ·
Replies
13
Views
4K
  • · Replies 13 ·
Replies
13
Views
3K
  • · Replies 11 ·
Replies
11
Views
2K