# Continuity problems for my Analysis class

I am having a lot of difficulty on my continuity problems for my Analysis class.

1. Prove that (f O g)(x) = f(g(x)) is continuous at any point p in R in three ways a.) Using the episolon delta definition of continuity, b.) using the sequence definition of continuity, and c.) using the open set definition of continuity.

2. Prove that if U is an open set in R, then its inverse is open.

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tiny-tim
Homework Helper
Hi LauraLovies!

(I assume f and g are both continuous? and have a delta: δ and an epsilon: ε )

Show us what you've tried, and where you're stuck, and then we'll know how to help!

f and g are both continuous so i know that there exists some $$\epsilon > 0 and greater than zero that fulfills the continuity definition. It just seems to obvious to me that i dont even know where to start. \delta$$

tiny-tim
Homework Helper
f and g are both continuous so i know that there exists some \epsilon > 0 and greater than zero that fulfills the continuity definition. It just seems to obvious to me that i dont even know where to start. \delta
Start with an εf and δf, and an εg and δg, and then construct a proof using a new ε and δ based on them.

lurflurf
Homework Helper

Which sequence definition? that lim f(x_n)=f(lim x_m)?
The general idea adaptible to the cases is that we desire
f(g(x+h))-f(x)=f(g(x)+[g(x+h)-g(x)])-f(x)
be small when h is