Y-Simple Region

Y-Simple Definition

A region $R\subset {\mathbb{R}}^2$ is y-simple if there are continuous functions ${\varphi }_1$ and ${\varphi }_2:[a,b]\to \mathbb{R}$ s.t: $R=\{(x,y):a\le x\le b\vee {\varphi }_1(x)\le y\le {\varphi }_2(x)\}$

Example

Intuition

There are curves bounding y