Open ball
= Open ball
In a <metric space>, the <open ball> of radius $r>0$ about $x$ is $\{y:d(x,y)<r\}$; it is the open-boundary convention for a <ball (mathematics)>.
= Open ball
In a <metric space>, the <open ball> of radius $r>0$ about $x$ is $\{y:d(x,y)<r\}$; it is the open-boundary convention for a <ball (mathematics)>.