3 thoughts on “[Bài Yosheph hỏi] Một số kết quả về đường tròn Ơle”

  1. 3. It is well-known that radius of nine point circle is equal to R/2, where R is radius of circumcircle of the triangle ABC. But area of ABC is equal to abc/4R, we are done.

  2. Because F has barycentrics a(1 – cos(B – C)) : b(1 – cos(C – A)) : c(1 – cos(A – B)) we are done.😛

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