What is vectors straddle a plane mean? There is a condition in a paper, saying that two vectors straddle a plane. How can we transfer this condition to a equation? Because I have another 5 equations and need this one to solve 6 unknowns. Thanks. Here is a figure for it. The vector $ \alpha $ and $\beta $ straddle the reference plane. Assume we know the function of the plane. !the vector \\alpha and \\beta straddle the reference plane

I would guess that it means that if $N$ is the normal vector to the plane, then the dot products $N \cdot \alpha$ and $N \cdot \beta$ have opposite signs. In other words, $\alpha$ and $\beta$ are on opposite sides of the plane.