Goldener Schnitt, Goldene Zahl | Berechnung, Herleitung

Whole-channel inclusion: MathePeter is an honest teaching channel (title sample + 3 transcripts read: All three samples lack transcripts, but titles/descriptions match the channel's consistent pattern of structured math problem-solving lectures, supporting the 'whole' verdict from the title sample.); this title passed a strict title check (sonnet) after a labelling pass.