http://www.ams.org/journals/mcom/1943-01-002/
Hayashi, Takao. 1997. Aryabhaa's Rule and Table for Sine-Differences. Historia Mathematica 24, no. 4 (November): 396-406. doi:10.1006/hmat.1997.2160.
Al-Biruni 의 업적
1939년 오일러 '새로운 형태의 진동에 대하여(De novo genere oscillatonum)' 출판 http://www.math.dartmouth.edu/~euler/pages/E126.html
Ptolemy was well aware of the new possibilities, because finding the distance between two stars was equivalent to measuring an arc of a circle, and he adapted the spherical geometry for use with tables of chords. http://nrich.maths.org/6853&part=
Of course, many of the astronomical calculations Ptolemy needed to perform concerned the angular distances between celestial bodies or, in other words, the positions of bodies on a spherical surface, for which spherical trigonometry is appropriate. Here, too, Ptolemy could use his table of chords.
While many new aspects of trigonometry were being discovered, the chord, sine, versine and cosine were developed in the investigation of astronomical problems, and conceived of as properties of angles at the centre of the heavenly sphere. In contrast, tangent and cotangent properties were derived from the measurement of shadows of a gnomon and the problems of telling the time. http://nrich.maths.org/6908&part=
The sine formula for spherical triangleswas used to good effect by the famous Islamic scholar al-B¯ır¯un¯ı with his solution to the qibla problem, this being to
determine the direction in which Mecca was closest from a given location on the Earth, i.e. along a great circle
시간과 주기운동 http://en.wikipedia.org/wiki/Atomic_clock
http://en.wikipedia.org/wiki/Spring_%28device%29
시계종류 : sundial, water, divisional time, pendulum, quartz, atomic clock http://www.youtube.com/watch?v=4T8uyD0AvzI
MOUSSA, ALI. 2010. The Trigonometric Functions, as They Were in the Arabic-Islamic Civilization. Arabic Sciences and Philosophy 20, no. 01: 93-104. doi:10.1017/S0957423909990099.
A Note on the History of Trigonometric Functions