Consider x1,…,xn vectors lying in Rn. Also, consider positive numbers α1,…,αn. Consider n spheres with center as xi and radii αi. How do I check the set of solutions to the set of equations
||x−xi||2=αi , ∀i
is non-empty. Is this problem studied in literature?
Answer
The question is well-studied. For example, you can read this.
One of the methods works like this:
Rewrite your equation as
2xix=x2+x2i−α2i.
Find x in form x=ru+v, where r=x2, u is the solution of 2xiu=1, v is the solution of 2xiv=x2i−α2i. Then
r=x2=(ru+v)2=r2u2+2uvr+v2
is a quadratic equation on r. If this equation has roots, then your n spheres have a common point.
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