Geometry textbook symbols

• Many crime fiction protagonists, briefly
• Detectives for hire, for short
• Greek consonants used in circle formulas
• Pastries?
• Magnum and others: Abbr.
• Greek letters used in geometry
• TV's Rockford et al
• Circle ratios
• Symbols used in angle measurement

Wiktionary Word definitions in Wiktionary
n. (plural of pi English)