Join the USAMO Guide Discord Server. Regular updates are posted there!

Let me Join!
Dismiss

Berkeley Math Circle Monthly Contest 4 #0jgf

Berkeley Math Circle Monthly Contest 4Hard

From module Angle Chasing Mastery

Community difficultyNo ratings yetBe the first to rate this problem.
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.
TangentsConcurrency and CollinearityAngle chasing

Problem

Problem: Let ABAB and CDCD be two nonperpendicular diameters of a circle centered at OO, and let QQ be the reflection of DD about ABAB. The tangent at BB meets ACAC at PP, and DPDP meets the circle again at EE. Prove that lines AEAE, BPBP, and CQCQ are concurrent.

← Back to all problems