Which of the following subsets of $\mathbb{R}^2$ are compact?
- (a) $\left\{ (x, y) : xy = 1 \right\} $
- (b) $\left\{ (x, y) : x^{2/3} + y^{2/3} = 1 \right\}$
- (c) $\left\{(x, y) : x^2 + y^2 < 1\right\}$
clearly a and c are not compact. not sure about b