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Alex Flint
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Lattice points close to a line

Take a sheet of grid paper and draw a straight line in any direction from the origin. What is the closest non-zero grid point $\boldsymbol{p}\in\mathbb{Z}^2$ within a distance $\epsilon>0$ of the line?

I have been unable to construct an example where the distance is large for any $\epsilon$. I would like to prove the following:

$\forall \epsilon>0 ~~ \exists R>0 ~~ \forall \boldsymbol{v} \in \mathbb{R}^2 ~~ \exists\boldsymbol{q}\in\mathbb{Z}^2, \|\boldsymbol{q}\| < R$ such that:

$\frac{|p_x v_y - p_y v_x|}{\|\boldsymbol{v}\|}<\epsilon$

where the LHS is the point-line distance.

Alex Flint
  • 561
  • 4
  • 18