Equivalence relation $f\sim g \iff f(n)=g(n)$

129 Views Asked by At

I have this equivalence relation defined on $\mathbb{N}$ and $f\sim g \iff f(n)=g(n)$ for some $n$.

I was testing this relation for reflexivity, symmetry and transitivity:

1) It is reflective since $f(n)=f(n)$

2) If $f(n)=g(n)$ then $g(n)=f(n)$, so symmetric

3) But for transitivity I think it fails, however I cannot find a counter example for this to work.

Can anyone point me in the right direction?

Context: Let S denote the set of real-valued functions on N. For each relation given below, determine whether it is an equivalence relation. If it is not an equivalence relation, then indicate an axiom – reflexivity, symmetry, or transitivity – which fails.

1

There are 1 best solutions below

1
On BEST ANSWER

Choose $$f(n)=1,$$ $$g(n)=1\text{ for }n=1,\qquad g(n)=0\text{ otherwise}$$ and $$h(n)=0.$$

This is a counterexample for transitivity as $f\sim g$ (choose $n=1$) and $g\sim h$ (choose e.g. $n=2$), but there exists no $n\in\mathbb N$ so that $f(n)=h(n)$.