Mathematics in Ancient and Medieval India c6.s10.1

c6.s10.1

Mahāvīra enlists three varieties of triangles (equi-lateral, isosceles, and scalene), five varieties of quadrilaterals (equilateral, equidichastic, equibilateral, equitrilateral and inequilateral) and eight varieties of curvilinear figures (circle, semi-circle, ellipse, conchi-form area, concave circle, convex circle, out-lying annulus, and in-lying annulus), while Śrīdhara takes the primary plane figures to be ten in number. They are rectangular (*āyata*), equilateral (*sama bhuja*), equi-bilateral (*dvi-sama bhuja*), equi-trilateral (*tri-sama bhuja*), the inequilateral quadrilateral (*visamabhuja-caturaśra*), the equilateral triangle, the scalene triangle, the isosceles triangle, the circle (*vṛtta*) and the segment of a circle (*vṛtta cāpa*).² Nārāyaṇa’s list of plane figures are also ten in numbers though he has replaced ‘the segment of a circle’ from the list of Śrīdhara by the “conch-figure”. According to Śrīdhara the area of these figures are determined by their own rules, and the areas of other figures are determined by considering their shapes in terms of the plane figures.