135 the (planet's) own epicycles (for the beginnings of the odd and even quadrants) and then divide (the product) by the radius; and apply the result (thus obtained) to the (planet's) epicycle (for the beginning of the current quadrant). Subtract (that result), when the epicycle for (the beginning of) the current quadrant is greater; add (that result), when the epicycle for (the beginning of) the current quadrant is smaller. Thus is obtained the (planet's) corrected epicycle.¹ In the case of the Sun and the Moon, which move around the Earth, we have seen that only one epicycle is contemplated which is meant to account for the eccentricity of the orbit. In the case of the planets, Mars, Mercury, Jupiter, Venus, and Saturn, which revolve round the Sun, two kinds of epicycles are envisaged, (i) manda, and (ii) ghra. We shall presently see how these epicycles are utilized to explain the motion of the planets. CORRECTED EPICYCLE Unlike the mean epicycle for the Sun or Moon, the manda and sighra epicycles for Mars, etc., are supposed to vary from place to place. Their values at the beginnings of the odd and even quadrants are given in the seventh chapter. Those for any other point of the. orbit are determined by the method taught in the stanza under consideration. Let and be the epicycles (manda or sighra) of a planet for the beginnings of the odd and even quadrants respectively. Then (1) if the planet be in the first quadrant (of the kendra), say at P, and its kendra be 0, epicycle at P - (B a + -α) x Rsin 0 R (dB) x Rsin () R (when d<B) (when α>B) and (2) if the planet be in the second quadrant (of the kendra), say at Q, and its kendra be 90° + +, ¹ This rule occurs also in Susi, ii. 38 and Sise, iii. 22. a Stanzas 13-16.
