Problem:
Given a triangle , we draw three circles with respective diameters , , and . Prove that there exists a point that is inside all three circles.
Problem:
Given a triangle , we draw three circles with respective diameters , , and . Prove that there exists a point that is inside all three circles.
Solution:
We claim that the center of the triangle's inscribed circle is such a point. To see this, note that
Thus is obtuse and if we drop a perpendicular from to , then lies on the extension of ray . The circle with diameter passes through since , and thus , an interior point of chord , lies inside the circle. By symmetry, we can conclude that lies inside the other two circles as well.