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1. Al Kashi

   Linked via "chords"

   Trigonometry
   Al-Kashi is often credited as the first to explicitly write the trigonometric functions (sine, cosine, tangent) as ratios of sides of a right triangle, rather than relying on lengths of chords in a circle, as was common in earlier Greek and Indian traditions.
   His tables, compiled for the Zij-i Sultani, tabulated sine and tangent va…

2. Ellipse

   Linked via "chord"

   Latus Rectum
   The latus rectum is a chord passing through one focus, perpendicular to the major axis. Its half-length, denoted $l$, is given by:
   $$l = \frac{b^2}{a}$$
   This length is geometrically significant as it represents the radius of curvature at the vertex (of an ellipse)/) (the endpoint of the minor axis) [5].