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

330 Place the Śaṅku at the point of intersection of the Bhuja and shadow and holding the Nalaka along the join of the top of Śaṅku and the point, the planet could be seen in a basin of water placed at the point. Comm. Let P be the planet casting the shadow AC of the gnomon AB. C the extremity of the shadow is the point of intersection of the shadow and the Bhuja. Though we have shown the gnomon in the position AB, it need not have been placed there in as much as we have the computed magnitudes of the shadow, the Bhuja and the Koti. Now we are directed to place the Śaṅku act- ually at C the point of intersection of the shadow and the Bhuja. Thus CD is the Śaṅku. Since CD=AB and and both are vertical evidently Δs DBA and DCB are congruent. Hence DĈB = DÂB. But DĈB = zenith- distance of the planet and as such is equal to BÂD (also the zenith-distance of the planet) ∴ DÂB = BÂP. Hence if a tray of water is placed at A, the planet will be visible as seen through DE, the Nalaka since the angle DAB is the angle of incidence and BÂP the angle of reflection are equal. Verse 109. The planet is to be shown to the king, who has an eye of appreciation for the same, either direct- ly (as shown in fig. 62) in the sky or through water as shown in the fig. 63, having finished the preliminaries indicated. Comm. Clear. End of the Tripraśnādhyāya.