when is a point inside a triangle

Suppose $u,v$ are vectors in ${ℝ}^2$, and

$$x=su+tv$$

for some $s,t\in ℝ$. Then $x$ is in the triangle spanned by $u$ and $v$ and the origin if and only if

$$s,t\ge 0,s+t\le 1.$$

Title	when is a point inside a triangle
Canonical name	WhenIsAPointInsideATriangle
Date of creation	2013-03-22 15:22:22
Last modified on	2013-03-22 15:22:22
Owner	matte (1858)
Last modified by	matte (1858)
Numerical id	5
Author	matte (1858)
Entry type	Theorem
Classification	msc 51-00
Related topic	WhenIsAPointInsideAPolygon