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MA/ AA_1+ MB/ BB_1> 2 MG/ GG_1

Source: 1987 Greece MO Grade XI p4

September 6, 2024
geometrygeometric inequality

Problem Statement

Let A,BA,B be two points interior of circle C(O,R)C(O,R) and MM a point on the circle. Let A1,B1A_1,B_1 be the intersections of the circle with lines MAMA,MBMB respectively. Let GG be the midpoint of ABABand G1=CMGG_1= C\cap MG. Prove thatMAAA1+MBBB1>2MGGG1\frac{MA}{AA_1}+ \frac{MB}{BB_1}> 2\frac{MG}{GG_1}