Historical clue formulations

• Trigonometric ratio — 2012-06-25
• Curve-cutting line — 2011-09-24
• Trig ratio — 2011-01-23
• Cosine's reciprocal — 2010-12-21
• Right triangle ratio — 2007-02-28
• Trigonometric ratio — 2006-09-07
• Trig function — 2005-01-02
• Trigonometric ratio — 2004-02-16
• Line intersecting a curve — 2002-04-20
• Trigonometry ratio — 1999-07-13
• Trigonometry ratio — 1999-07-06
• Intersecting line — 1996-12-27
• Trigonometric function — 1994-05-02
• Cosine's reciprocal — 1994-04-17