Video narration
Batul britter samne dariye chitkar kore uthlo, "Gopalda! Chord-ta shoman dui bhag hobe kibhabe?" Gopal hente eshe bollo, "Centre-ke kaje lagao!" Shuru holo detective investigation. Brittter centre O, chord AB, ar O theke AB-te namlo OM, ekebare perpendicular, orthat shomokon kore. M-i ekhon shondehobhajon midpoint, majher bindu. Prothom clue: OA = OB, karon dutoi radius. Ditiyo clue: OM = OM, eki common side. Tritiyo clue? angle OMA ar angle OMB, dutoi 90 degree. Ebar Gopal bollo, "Shob clue eksathe miliye dekho!" Tai triangle OMA ebong OMB congruent, mane tara hubohu shoman. Ar tokhoni rohoshyer shomadhan: AM = MB! Batul chokh boro kore bollo, "Maths to detective story!" Gopal hese bollo, "Thik tai, perpendicular-tai decisive clue; oitai dui pashke shoman kore." Ebar notun chord CD. Jodi OM perpendicular CD hoy, bolo to, MC ar MD-er relation ki? Ei detective case-er shesh clue mone rekho, centre theke chord-e perpendicular namlei chord dui shoman bhag: AM = MB!