Toolkit 59Ptolemy's TheoremA quadrilateral ABCDABCDABCD is cyclic if and only if:AB⋅CD+AD⋅BC=AC⋅BDAB\cdot CD+AD\cdot BC=AC\cdot BDAB⋅CD+AD⋅BC=AC⋅BDRelated ProblemsCoreAMC 12A 2024 (Problem 19)AMC 12B 2025 (Problem 25)
