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MathNet 2013 Question 57

Math Olympiad Vault · MathNet 2013

Question 57

Let $P$ be a point in the interior of the acute triangle $ABC$ and let $D$, $E$, $F$ be respectively the intercepts of lines $AP$, $BP$, $CP$ with the sides $BC$, $CA$, $AB$.

a) Prove that the area of the triangle $DEF$ is not greater than a quarter of the area of triangle $ABC$.

b) Prove that the inradius of $DEF$ is not greater than a quarter of the inradius of triangle $ABC$.

Question illustration