Geometry · Isosceles triangles · Angle chasing · Right triangles · Contact triangle

Problem 2, 2023

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NationalEnter the answer

In triangle \(ABC\) the angle at \(A\) is a right angle. Points \(D\), \(E\) and \(F\) are chosen on the sides \(AB\), \(BC\) and \(CA\) respectively, so that

\[ |BD| = |BE| \qquad\text{and}\qquad |CF| = |CE| , \]

as in the figure. How many degrees does the angle \(\angle FED\) measure?

A B C D E F ?
The two marked pairs of equal segments hang off the vertices \(B\) and \(C\).
  1. A \(30\)
  2. B \(37.5\)
  3. C \(45\)
  4. D \(52.5\)
  5. E It cannot be determined, because the answer depends on the size of \(\angle CBA\).

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Slovenian High School Mathematics Competition for Vega Awards (MaSSA), drzavno (national) round 2023, 1. letnik, category A, problem A2. Organized by DMFA Slovenije (Society of Mathematicians, Physicists and Astronomers of Slovenia). Source