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HMMT February 2025 #0l6x

HMMT February 2025Hard

From module Angle Chasing Mastery

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Understand the scale
Scale 0.5: Easiest math competition problems, often solvable even for early middle school students without experience. 1: Problems strictly for beginners, often at a moderate middle school level. 1.5: Problems for stronger beginner students, on the level of the middling problems in most middle school contests. 2: For motivated beginners, harder questions from the previous categories. 2.5: More advanced beginner problems, hardest questions from previous categories. 3: Early intermediate problems that require more creative thinking. 3.5: Tougher early intermediate problems that consistently stretch into higher-level creative thinking or conceptual knowledge. 4: Intermediate-level problems. 4.5: Upper intermediate problems approaching the upper bound for non-invitational sprint math competitions. 5: More difficult AIME problems or simple proof-based Olympiad-style problems. 6: High-level AIME-styled questions or introductory Olympiad-level questions. 7: Tougher Olympiad-level questions, may require more technical knowledge. 8: High-level Olympiad-level questions. 9: Expert Olympiad-level questions. 9.5: The hardest problems appearing on Olympiads which the strongest students could reasonably solve. 10: Historically notorious problems, generally unsuitable for even very hard competitions because they are exceedingly tedious, long, and difficult.
Complex numbers in geometryAngle chasingComplex numbersPolynomial operationsIntermediate Value Theorem

Problem

Problem:

Complex numbers ω1\omega_{1}, …\ldots, ωn\omega_{n} each have magnitude 11. Let zz be a complex number distinct from ω1\omega_{1}, …\ldots, ωn\omega_{n} such that

z+ω1z−ω1+⋯+z+ωnz−ωn=0.\frac{z + \omega_{1}}{z - \omega_{1}} + \dots + \frac{z + \omega_{n}}{z - \omega_{n}} = 0.

Prove that ∣z∣=1|z| = 1.

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