# get position of point given distance from other points?

I have a 2 points i know the distance between them with a 3rd points. how to get the position of the 3rd point given other distances with the other two points ?

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Given only this information, you generally can't know the specific point. That third point will be at an intersection of two circles--one centered around each of the other two points. In particular, let's call your first two points $a,b$ and the point you're looking for $c.$ Let $r_{ab}$ be the distance from point $a$ to point $b$, and let $r_{ac},r_{bc}$ be the desired respective distances from $a,b$ to $c$. What we're dealing with, then, is circles around $a$ and $b$ of respective radii $r_{ac}$ and $r_{bc}$.
Now, if two of $r_{ab},r_{ac},r_{bc}$ add up to the third, then there is exactly one point of intersection of the two circles--and that is our point $c$. If two of $r_{ab},r_{ac},r_{bc}$ add up to some number that is less than the third, then the circles don't intersect at all, and there is no such point $c$. Otherwise, there will be two points of intersection of the circles, and $c$ will be one of those, but (as I said) there's no way to know which, given only this information.