keywords: Math, check if a point is inside a rectangle or triangle

##### Rectangle

https://math.stackexchange.com/questions/190111/how-to-check-if-a-point-is-inside-a-rectangle

##### Triangle

Check whether a point is within a 3D Triangle
https://math.stackexchange.com/questions/4322/check-whether-a-point-is-within-a-3d-triangle

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