सिद्धान्तशिरोमणि: गणिताध्याय (भास्कराचार्य - ग्रहगणित, मध्यमाधिकार व स्पष्टाधिकार सटीक)

542 zero ?" The answer is t (a + b) / Adya - Anya which gives the time after which Vaidhṛti is likely to occur. Suppose a and b the declinations observed at a particular moment, are one north and and the other south. Compute their difference a - b; after a few ghatis or days again from the difference of the declinations c and d ie. c - d. If c - d < a - b then Vaidhṛti is going to occur, otherwise it has elapsed. This is so because the difference has to vanish for Vaidhṛti to occur. Viewing the situation algebraically, ie. construing northern declination to be positive and southern negative, we could have laid down only one criterion, instead of separating the issues and stipulating separate criteria. Proceeding on this basis, suppose the the Sun and the Moon are one in the first quadrant and the other in the second. Here both declinations are therefore positive. Compute their difference a - b; compute again the difference of c and d which are again northern declinations observed after a few ghatis or days. If c - d < a - b then Vyatīpāta is going to occur. Now take a case when one of a and b is north and the other south ; so also c and d. We are talking of a, c to be in the first quadrant and b, d in the fourth quadrant. Even now if c - d < a - b Vyatīpāta is going to occur. Thus there is no need to stipulate "Sum or difference". Difference alone counts now, because difference of one positive and the other negative quantities means sum only. Thus in the case of Vyatīpāta difference should tend to zero, whether both the declinations are north, or one north and the other south. Similarly in the case of Vaidhṛti the sum should tend to zero because the algebraic sum of one positive northern declination and the other negative southern declination