MathDB
Geo with trigo bash

Source: 2023 Turkey Tst D1 P1

March 29, 2023
geometrytrapezoidcircumcircle

Problem Statement

Let ABCDABCD be a trapezoid with AB∥CDAB \parallel CD. A point TT which is inside the trapezoid satisfies ∠ATD=∠CTB \angle ATD = \angle CTB. Let line ATAT intersects circumcircle of ACDACD at KK and line BTBT intersects circumcircle of BCDBCD at LL.(K≠AK \neq A , L≠BL \neq B) Prove that KL∥ABKL \parallel AB.
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