Erdös-Mordell Inequality

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Pakkinee Chitsakul


The article shows the proof of Erdös-Mordell inequality for any triangle, there exist a point inside the triangle which the sum of the orthogonal projection from the point to all three sides is less than or equal to half of the sum of the distance from the point to the three vertices of the triangle. The proof is based on the work of Claudi Alsina and Roger B. Nelson which published in Forum Geometricorum V7(2007) 99-102.

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Chitsakul, P. (2018). Erdös-Mordell Inequality. Mathematical Journal by The Mathematical Association of Thailand Under The Patronage of His Majesty The King, 62(692), 19–30. Retrieved from
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