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right angle wanted, bases of inscirbed trapezoid AB =3 CD

Source: Tournament of Towns, Junior A-Level Paper, Spring 2020 , p5

June 4, 2020
right angletrapezoidequal segmentstrapeziumgeometry

Problem Statement

Let ABCDABCD be an inscribed trapezoid. The base ABAB is 33 times longer than CDCD. Tangents to the circumscribed circle at the points AA and CC intersect at the point KK. Prove that the angle KDAKDA is a right angle.
Alexandr Yuran
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