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circle tangent to circumcircle

Source: Spanish Mathematical Olympiad 1977 P6

December 23, 2022
geometrytangent circlescircumcircle

Problem Statement

A triangle ABCABC is considered, and let DD be the intersection point of the angle bisector corresponding to angle AA with side BCBC. Prove that the circumcircle that passes through AA and is tangent to line BCBC at DD, it is also tangent to the circle circumscribed around triangle ABCABC.