Set theory: A = ⟨1,→⟩, is '→' equivalent to '∞'?

Question

I'm reading an introductory mathematics book and came across the following syntax:

A = ⟨1,→⟩

B = {1,2,3}

The question:

Find A ∩ B and A ∪ B

Should I assume A = ⟨1,→⟩ = ⟨1,∞⟩?

Answer 1

Yes, $\langle 1,\to\rangle$ is another way of writing $\langle 1,\infty\rangle$ (it is what students learn in high school here in Norway, for instance). Also, note that using angle brackets to denote open intervals is somewhat uncommon. It is much more common to see $(1,\infty)$, and to a certain extent $]1,\infty[$.