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A fixed ratio

Source: Iran 3rd round 2012-Geometry exam-P1

September 20, 2012
ratiogeometrycircumcircletrigonometryparallelogramgeometry proposed

Problem Statement

Fixed points BB and CC are on a fixed circle ω\omega and point AA varies on this circle. We call the midpoint of arc BCBC (not containing AA) DD and the orthocenter of the triangle ABCABC, HH. Line DHDH intersects circle ω\omega again in KK. Tangent in AA to circumcircle of triangle AKHAKH intersects line DHDH and circle ω\omega again in LL and MM respectively. Prove that the value of ALAM\frac{AL}{AM} is constant.
Proposed by Mehdi E'tesami Fard