Open set

[kevin01]

I want show the following set is open by the definition of the open set,( i know how show this with the inverse image of set)
?={(?,?,?)∈ℝ^3∣?>?>?}.
Thank you

 

[Dr.Peterson]

Please let us know what help you need, by showing your work. If you haven't even started, you can at least state the definition you are using, and make an attempt to apply that definition to this particular set, to see what you need to prove.

 

[pka]

I want show the following set is open by the definition of the open set,( i know how show this with the inverse image of set) \(\mathcal{?}=\{(?,?,?)∈ℝ^3∣?>?>?\}\).

Can you at least give us the definition of what it means to say that \(\mathcal{A}\) is an open set.