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vs. 22-23 ) the east (ii) The Rsine of that are, which is equal to the distance between west line and the rising-setting line of the heavenly body concerned. To avoid this ambiguity, we have translated the term agra by *(the arc (the Rsine of) aga', according as it is used in the former or 1atter sense. hcrnever the qualifying phrases have not been used the mean ing should be understood from the context A rule for calculating the prime vertical altitude of the Sun and the corresponding shadow of the grnommon: 22-23. The Rsine of the Sun's northern declimation, when less than the Rsine of the latitude, multiplied by the radius should be divided by the Rsine of the latitude : the result is the Rsine of the altitude of the Sun when it is on the prime vertical The sguare root of the square of the radius diminished by that of the Rsine of the Sun's altitude (obtained above) when multi plied by twelve and divided by the ( same) Rsine of the Sun's altitude gives the shadow (of the gnommon corresponding to the Sun on the prime vertical). 0 ) That is, when the Sun is on the prime vertical, () (ii) Rsin a = where a is the Sun's the place Rsin 8 Shadow of the gnommon 12 x R altitude, ४ the Sun's declination, and * the latitude of In Fig. 6 on page 50, let S denote the position of the Sun when it is on the prime vertical, SA and SB the perpendiculars from S on the east-west and rising-setting lines respectively, and C the point where SB meets the |ime joining the points of intersection of the Sun's diurnal circle and the six o'clock circle. Since SB 1ies in the plane of the diurmal circle and AC in the plane of the six o'clock circle, and the two circles are at right angles, therefore AC and SB are at right angles