Mathematics in Ancient and Medieval India c6.s9.16

c6.s9.16

*eka-karṇa* (a geometrical figure of equal angles), *dvi-karṇa* (a geometrical figure of two equal angles), *tri-karṇa* (triangle) etc. based on relations between the angles. In the *Sūryaprajñapati* (300 B. C.) both these types are represented respectively by *sama-caturasra* (square), *viṣama-caturasra* (quadrilateral other than square) having side basis, and *sama-catuṣkoṇa* (square or rectangle), *viṣama-catuṣkoṇa* (quadriangle other than square or rectangle) having angle basis. Both Āryabhaṭa I (c. 476 A.D.) and Brahmagupta (628 A. D.) however used the side basis depending on the terms *tribhuja*, *caturbhūja* and also *caturarasra* (square), *viṣama-caturasra* (quadrilateral having all unequal sides).