Let , , denote the tangent points of the incircle of with the sides , , , respectively. Let be the midpoint of the segment . Let be the intersection point of the circle passing through , , and the segment , be the intersection point of the circle passing through , , and the segment .
Prove that the circle passing through , , touches the line .
(V. Voinov)
Solution
Let I be the incenter of the triangle ABC. Let denote the circle passing through , , . We have
Therefore, lies on . So, to prove that touches it suffices to show that .

Since and , it follows that and is the bisector of the angle , i.e., the points , , lie on the same line.
We have
Since the triangle is the right-angled triangle and , we have . Since , we obtain . By the Power of a Point Theorem, the circle passing through the points , , touches the line at , then . From (1) it follows that as required.
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