I Dare You To Take A Special Case! Part 2

Geometry Level 5

Let Γ 1 \Gamma_1 be the circumcircle of Δ A B C \Delta ABC and Γ 2 \Gamma_2 be the circumcircle of Δ D E F \Delta DEF where D , E , F D,E,F are the foot of the altitudes of Δ A B C \Delta ABC .

If Γ 1 \Gamma_1 cuts Γ 2 \Gamma_2 orthogonally, compute the value of the following expression upto three decimal places:

cyc cos 2 A \sum_\text{cyc} \cos 2A

Notations:

  • A A denotes B A C \angle BAC . B B and C C are defined similarly.
  • cyc \displaystyle \sum_\text{cyc} denotes cyclic summation.

This problem is part of my set: Geometry


The answer is 1.000.

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1 solution

Ahmad Saad
May 5, 2016

Exactly the intended solution! (+1)

A Former Brilliant Member - 5 years, 1 month ago

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