The Shulbasutras of Baudhayana, Apastamba, Katyayana and Manava: With Text, English Translation and Commentary c8.t18.13

c8.t18.13

**1.4-1.5.** *Theorem of square on the diagonal.* The rule says, AB²+BC²=AC², where AB and BC are the sides of a rectangle ABCD. We have discussed this *sūtra* in detail under *Bśl.* 1.12 and 1.13. Only the last line of *Āśl.* 1.4, which contains the term *tābhirjñeyābhi* requires to be explained. According to Bürka, "the construction (found in *Āśl.* 1.2 and 1.3) has been taught by means of (the application of) these (*akṣṇayārajju*, *pārśvamānī* and *tiryaṅmānī* of a rectangle), of course, by means of such as are recognizable (i.e. which can be expressed in recognizable numbers)." *jñā* means 'to know'. Various terms like *jñātumsakti*, *iti vijñāyate*, *tābhirjñeyābhi* have been used by the *śulbakāras*. According to Datta b, these can be interpreted as "known from the ancient scriptures".