Brahmasphutasiddhanta (Complete Sanskrit Text)

The method for its calculation is stated in the Gaṇitādhyāya Chapter on Mathematics of the Siddhāntaśiromaṇi Crest of Doctrines under the Spuṭādhikāra Chapter on Correction. From Bhāskara's statement, "The son of Jiṣṇu Brahmagupta spoke of the Moon and Sun’s eclipse and the tithi lunar day through repeated correction," it is known that the discoverer of this is Brahmagupta himself. The bhogyakhaṇḍa-sphuṭīkaraṇa correction of the consumable portion/arc stated by Bhāskarācārya is also based on what Brahmagupta said in the Dhyānagrahopadeśādhyāya Chapter on Instruction of Planet Perception of the Brahmasphuṭasiddhānta; no other teacher has written anything in that regard. Kamalakara, in the Siddhāntatattvaviveka, has only refuted the bhogyakhaṇḍa correction stated by Bhāskara. In reality, the refutation by Kamalakara is not correct. In the Tripraśnādhikāra Chapter on Three Questions of the Brahmasphuṭasiddhānta, regarding the determination of direction: "The difference in direction of the two points of equal shadow, the east-west line; from the middle of that, by declination, the other śaṅku-tala gnomon-plane," in this, why a difference arises in determining direction by declination is why the difference between the gnomon-circle tips, which was derived by Caturvedācārya, was accepted by Śrīpati with the statement "difference of the solar declination-sine at the time of shadow exit and entry," and subsequently by Bhāskara with "the difference between the declination-sines of those times." In calculating the mandaphala, in reality, the mandaphala is achieved through the mandakarṇa slow hypotenuse ratio. Although Bhāskara did not present his own view here, he still accepted Brahmagupta's view in calculating the apparent Sun and Moon hypotenuse during a lunar eclipse by saying "to be calculated like the slow-hypotenuse calculation," which indicates the uniqueness of Brahmagupta's statement. Lallācārya performed the calculation of valana deflection and dṛkkarma visual correction using the utkramajyā inverse sine, and targeting the commentary of Caturvedācārya that "here, by the word jyā, the utkramajyā should be understood," Bhāskara said: "That jewel of a composition by Brahmagupta is considered otherwise by his followers."

"The yugas ages, manvantaras intervals of Manu, and kalpas aeons are spoken of as the measure of time in the scriptures.
Because they are not in the Romaka, therefore the Romaka is outside the scriptures."

(Brahmasphuṭasiddhānta Chapter 1)

By this statement of Brahmagupta, it is clear that the Romaka Siddhānta was composed by taking the foundation of some Western astronomer by the name of "Romaka." Among the ancient teachers, only Brahmagupta refutes the Romaka view. Varāhamihira, however, accepts the calculation of the ahargaṇa count of days and many other topics according to the Romaka Siddhānta. Brahmagupta, by saying:

"The planetary mathematics spoken by Brahmā, which became obsolete over a long time,
is clearly spoken of by the son of Jiṣṇu, Brahmagupta."

it is clear that he repaired the Brahma Siddhānta itself. This proves that a single, very ancient Brahma Siddhānta existed as their root. Brahmagupta, however:

"Those whose sight is blocked by the cataract of ignorance, who speak of a siddhānta other than the Brahma,
I will tell of the faults in their yuga beginnings."