Let we have an isosceles triangle ABC where $AB=BC$.
How to find parameters of a circular arc that (1) pass through points A and C, (2) such as AB and AC are tangents to this arc.
The arc parameters we need are: $R$ - radius of a circle that produces arc, and $\alpha$ - arc angle.
A possible solution can be to prolong the triangle sides and to find the circle inscribed into this bigger triangle that touches it into points $A$ and $C$. But how to deside to which length we nedd to prolong these sides?