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MathNet 2021 — Part 03 Question 35

Math Olympiad Vault · MathNet 2021 — Part 03

Question 35

We consider a triangle $ABC$ and a point $D$ on the extended line segment $AB$ on the side of $B$. The point $E$ lies on side $AC$ such that the angles $\angle DBC$ and $\angle DEC$ are equal. The intersection of $DE$ and $BC$ is $F$. Suppose that $|BF| = 2$, $|BD| = 3$, $|AE| = 4$, and $|AB| = 5$. (Attention: the picture has not been drawn to scale.)

Question illustration

a.
Prove that triangles $\triangle ABC$ and $\triangle AED$ are similar.

b.
Determine $|CF|$.