A History of the Kerala School of Hindu Astronomy (in Perspective) c8.s7.1

c8.s7.1

In the context of the continuity of astronomical tradition and the diligence with which its traditional exponents cultivated its study, a reference might be made here to certain other significant methodologies evolved and discoveries made by Kerala astronomers and mathematicians. The introduction of the *Kaṭapayādi* notation and the expression of astronomical data through mnemonic tables and verses composed with the help of this facile notation has already been noticed. In his table of sine-differences enumerated in the verse *makhi-bhakhi* etc. (*Gītika* 10), *Āryabhaṭa* gives only their rough values, correct to the minute. It is interesting that Govindasvāmin (*c.* 800-50) developed their evaluation still more accurately, correct to the second order of sexagesimal fractions, viz., seconds and thirds, which he gives in his *Bhāṣya* on *Mahabhāskarīya*. He also gives a formula for the derivation of the value of the last sine-difference when the tabular interval is halved. Developing the topic further, he enunciates also a rule for computing, from a given last sine-difference, the other sine-differences lying between 60° and 90°.¹