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The above formula for A has some inconsistency in its dimension. This problem, however, is easily resolved. Without violating its meter, one can interchange the two compounds, tāvatkytvā ('multiplied by itself) and vadanadalonanam (decreased by half the mouth') in Stanza 13, and we would have:
A={(1-7)*+()}}x2+4.
This emended formula reminds one of the formulas for the 'conch-shell-circle' (kambukāvítta/ sankhavrtta) given by Mahāvīra (Gaạitasārasaṁgraha 7.23 and 7.65-6, ca. AD 850) and by Nārāyaṇa (Gaạitakaumudī, kşetra 10-11, AD 1356). And quite interestingly, if we emend the first word, dvi-, of the second line of Stanza 13 to tri-, Vīrasena's formula would become equivalent to their formulas employing 3 for a.
Figure 4: Conch-shell-like plane figure
vadanārdhono vyāsas triguṇaḥ paridhis tu kambukāvịtte
65
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