Finding the distance between two Points on the circumference of a circle

circles

visualisation of my problem.

take a circle with the radius r and its center at (0, 0). If I have two points, A and B of which A is known and B is unknown, how can I calculate the position of B, if I know the distance on the circumference between the two Points?

in my visualisation, if I know A and h, how can I calculate B?

Best Answer

There is not a unique point which has the same distance from $\rm{A}$ as $\rm{B}$. So, you can find two points, say $\rm{B'}$ and $\rm{B''}$, such that $|\overline{\rm{AB'}}|=|\overline{\rm{AB''}}|$. Thus, we have the isosceles triangle $\rm{AB'B''}$, you know both its sides and the vertex between them.

Another way to see this problem is to find the common solutions of the two circles centered in $\rm{O} \equiv (0,0)$ and $\rm{A}$, having radius equal to $|\overline{\rm{OA}}|$ and $|\overline{\rm{AB'}}|$, respectively.