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

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Rule. If the Ahargaṇa be x days then the Śīghra will
be 4x° + (4x × 3') / 130 + Dhruvaka. Proof. For x days, the mean
motion is x × 4° + x × (0-5′-32″-18‴-28⁗). The second
part is taken to be 4x × 3° / 130 ie x × 12° / 130 = x × 6/65° for
6/65 of a degree = 0-5′-32″-18‴-"28"". The fraction 6/65 can
be seen to be a convergent of the remainder for 5′-32″-
18‴-28⁗ = 299077° / 3240000 = 1/(10 +) 1/(1 +) 1/(4 +) 1/(1 +) 1/9968 of which the
penultimate convergent is 6/65.
Verse 19. The Ahargaṇa divided by 12 and by 71
gives respectively the positive degrees and negative minutes
to be added to the Dhruvaka of Jupiter.
Comm. If x be the Ahargaṇa x° / 12 − x' / 71 + Dhruvaka =
Guru.
The mean daily motion of Jupiter is 0-4-59-9.9 = 0-5′
minus 0-0-0-50-51. Evidently 0-5′ × x = x° / 12. The
remainder 0-0-0-50-51 = 61′ / 4320 of which the continued
fraction is 1/(70 +) 1/(1 +) 1/4. A very approximate convergent
is 1/71 as given.
Verse 19 contd. To obtain the position of the Śīghra
of venus.
The Ahargaṇa multiplied by 10 and divided by 6 and
155 respectively gives degrees positive and negative to be
added to the Dhruvaka of Venus to give his position.
Comm. The formula is 10 x / 6 − 10 x / 155. The mean daily
motion of the Śīghra of Venus is 1°-36′-7″-44‴-35⁗ =