Euclidean ball
= Euclidean ball
This is a <ball (mathematics)> for the Euclidean metric.
The closed Euclidean ball of radius $R$ about $a\in\mathbb R^n$ is $\{x:\lVert x-a\rVert_2\leq R\}$; replacing $\leq$ by $<$ gives the open ball.
= Euclidean ball
This is a <ball (mathematics)> for the Euclidean metric.
The closed Euclidean ball of radius $R$ about $a\in\mathbb R^n$ is $\{x:\lVert x-a\rVert_2\leq R\}$; replacing $\leq$ by $<$ gives the open ball.