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

265
Fig. 45
and that passing through the top of the gnomon being
parallel planes cut the horizontal plane in parallel straight
lines. (This will be also proved analytically subsequently).
Hence LM = s. Now from the figure
LM / gL = AB / gA = H sin a / R ∴ gL = H sin a / Rs I
This gL is spoken of as Iṣṭa-Drikmandala palabhā
because it is the shadow on the equinoctial day in
any vertical. LN is the increment in the shadow on
account of declination and we have to compute this and
correlate gL and LN. For this refer to figs. 46 and 47.
In fig. 46, QRT is the equator, so that when the Sun is on
the equator on the equinoctial day in the direction given
by ZS, ZT is the zenith-distance. Let ZS be the zenith-
distance of the Sun in the same direction on any day
From the analogy of finding H sin δ from H sin λ, from
this figure
34