"The ' is a compendium of astronomy made up of cryptic rules in Sanskrit verse, with little explanation and no proofs... [N]umbers were written... in strings of words which conform to the poetic scheme... [A]lmost all...primitive sine functions [are] defined in terms of a circle whose radius, R, is not unity. We distinguish all these with from the modern sine function by the use of an intitial capital... explicitly displaying the parameter R when useful, as a subscript. In general, then, \mathrm{Sin}_R \theta \equiv R \sin \theta... and analogously for the other trigonometric functions..."