# [SOLVED]R^2 accumulation and open/closed

#### dwsmith

##### Well-known member
All points $(x,y)$ such that $x^2 - y^2 < 1$.

This set is open but I am not sure about the accumulation points.

#### CaptainBlack

##### Well-known member
All points $(x,y)$ such that $x^2 - y^2 < 1$.

This set is open but I am not sure about the accumulation points.
The set is the region of $$\mathbb{R}^2$$ between the branches of the hyperbola $$x^2-y^2=1$$. All the points on the hyperbola are accumulation points, so the set of accumulation points is $$\{(x,y)\in \mathbb{R}^2: x^2-y^2\le 1 \}$$

CB