ḍakhādyaka seem to differ much from those of the Āryabhaṭīya.[1] Is this to be taken as an indication that Brahmagupta here is following an older and a different Āryabhaṭa? If so the Brāhmasphuaṭasiddhānta gives no clear indication of the fact. Or is he following another work by the same Āryabhaṭa? According to Dīkṣit,[2] the Khaṇḍakhādyaka agrees in all essentials with the old form of the Sūryasiddhānta rather than with the Brāhmasphuaṭasiddhānta. Just as Brahmagupta composed two different works so Āryabhaṭa may have composed two works which represented two different points of view. The second work may have been cast in a traditional mold, may have been based on the old Sūryasiddhānta, or have formed a commentary upon it.
The Mahāsiddhānta of another Āryabhaṭa who lived in the tenth century or later declares (XIII, 14):
vṛddhāryabhaṭaproktāt siddhāntad yan mahākālāt |
pāṭhair gatam ucchedaṁ viśeṣitam tan mayā svoktyā ||
But this Mahāsiddhānta differs in so many particulars from the Āryabhaṭīyathat it is difficult to believe that the author of the Āryabhaṭīya can be the one referred to as Vṛddhāryabhaṭa unless he had composed another work which differed in many particulars from the Āryabhaṭīya. The matter needs careful investigation.[3]
