Historical clue formulations

• Geometers' calculations — 2026-04-15
• They're right at 90° — 2025-06-30
• Photographers' considerations — 2024-08-10
• 12 parts of a dodecagon — 2022-11-08
• Photographers' considerations — 2020-06-19
• Drops a line — 2016-09-25
• What intersecting lines create — 2010-08-22
• Perspectives — 2006-02-26
• Protractor measurements — 2006-01-15
• Some are right — 2001-05-02
• Aspects of problems — 2000-06-02