सिद्धान्तशिरोमणि: गणिताध्याय (भास्कराचार्य - ग्रहगणित, मध्यमाधिकार व स्पष्टाधिकार सटीक)

524 vertically with the help of a plumb-line. Draw a circle on the horizontal plane having the foot of the gnomon as the centre and any arbitrary radius. Draw the East-West and North - South diameters of the circle. The longitudes of the Sun when the shadow of the gnomon lies along the East - West diameter give the gola Sandhis. Note the direction of the shadow daily after the day when his shadow is along the East - West line. If the Sun rises thereafter a little towards North of the East point, then he is said to be in the uttara gola; his shadow will be a little south of the East - West line. The point at which the Sun thus begins to rise north of the east point, is the Meṣa gola Sandhi or the vernal equinox. Gradually the Sun goes on rising at points which are farther and farther away from the East point. When he has reached the extreme north point, ie when the gnomon's shadow is extreme south, he is at the Cancer. Similarly when he rises at the extreme South point on the horizon, he is at Capricorn. Bhāskara actually noted these four points and the longi- tudes cited above were given by him as the Gola Sandhis and Ayana Sandhis. Indirectly, he could know that the Ayanāṁśas at the time of his writing the book, were 11°. Verses 3 to 6. Speciality with respect to the Moon. Let the Hsine and Hcosine of the tropical longitude of the pāta (Rāhu the ascending node of the lunar orbit) as per the smaller table of Hsines when the radius is taken to be 120', be respectively multiplied by 123 and 7 and divided respectively by 4 and 12. The results are known as the Bāhuphala and Koṭiphala respectively. According as the tropical longitude of Rāhu ie λ be such that as 270° < λ < 90° or 90° < λ < 270°, the Bāhuphala is to be divided by 362 ± Kotiphala. Subtract the result from the Gola Sandhis and Ayana Sandhis of the Sun, to get those of the Moon.