# Points on a Unit Sphere

Geometry Level pending

Let $$x , y \in \mathbb{R}^3$$ be two points on the unit sphere, such that

$y = x + a$

where $$a \in \mathbb{R}^3$$, and $$|| a || \le 2$$. The locus of all points $$x$$ that satisfy the above equation is a circle. What is the radius of this circle?

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