Hallo everyone,
Do you know any simple formulas that are often unknown to many? For me, some can be mentioned are - Euler characteristic - 2-Ear Theorem - Pigeonhole - Fermat - Handshaking theorem - incenter formula of a triangle - harmonic series sum - pick theorem - Shoelace Formula - McNugget theorem - Caley Formula ... And what about you? Can you share some?
Thank you.