Let be a median in an acute triangle . Its extension intersect the circumcircle of at . Let be an altitude of , - its orthocenter. The rays and intersect at and respectively. Prove that the circumcircle of is tangent to .
(Khilko Danylo)
Let be a median in an acute triangle . Its extension intersect the circumcircle of at . Let be an altitude of , - its orthocenter. The rays and intersect at and respectively. Prove that the circumcircle of is tangent to .
(Khilko Danylo)
It suffices to show that (Fig. 14). Let us extend and intersect if with at . Then
So it is sufficient to show that .
Denote by the point such that is the diameter of . Then , so and . Then is a parallelogram, so passes through the point .
Then lies on , hence . Then the quadrilateral is inscribed. So . Suppose intersect secondly at . Then
Hence, , also , so we derive . Then