# Definition:Half-Plane/Open/Right

## Definition

Let $\PP$ be a Cartesian plane.

Let $\LL$ be the $y$-axis.

The open right half-plane $\HH_{\text {OR} }$ is the area of $\PP$ on the right of $\LL$.

That is, where $x > 0$:

$\HH_{\text {OR} } := \set {\tuple {x, y}: x \in \R_{>0} }$