Mathematics in Ancient and Medieval India c7.s2.59

c7.s2.59

$a. n-1S_r. (r+1)/(n-1) + b. n-1S_r$ when a, b and n are the 1st term, common difference and number of terms of an A. P. Nārāyaṇa represented the parallel sides of a trapezia by a-b/2 and nb+a-b/2 and the altitude by n. Arithmetic Progression with sum=0 are diagrammatically represented by joining two equal isosceles inverted triangles with their vertices.