The Astronomical Observatories of Jai Singh c6.s1.t1.36

c6.s1.t1.36

(b) The ‘quadrant of sines’ occupies the south-east quadrant and occurs in most instruments. In some instruments the vertical radius is divided into sixty equal parts, and lines parallel to the other radius are drawn to the circumference from each point of division (figure 12); in others, both radii are so divided and horizontal and vertical lines are drawn from each point of division (figure 8); in others, horizontal lines are drawn from each degree on the quadrant. The vertical and horizontal scales indicate the sines and cosines of the corresponding angles. In the description of the Zarqālī astrolabe below (p. 29) the use of these scales is explained in more detail. In some instruments arcs for 23½°, 30°, etc., are described.