पञ्चसिद्धान्तिका (आचार्य वराहमिहिर - सूर्य, रोमक, पौलिश, वासिष्ठ एवं पितामह सिद्धान्त)

V. 3 V. PAULISA MOON'S CUSPS 141
∴ M'C = SL × MM' ÷ LM', i.e. 'the result' = difference in declination × moon's latitude ÷ 'the
square root', (which is step iv).
Now for the additive or subtractive nature of 'the result':
If the Moon's ayana is northward, i.e. if the ecliptic is inclined northwards (as in fig. 1), the Moon
having south latitude, being at the end of a perpendicular to it, is lifted up. Therefore the Moon
projected at M' is projected at C, as it were, and the difference in longitude which is the distance
between S and M', is increased. So, in this case, 'the result' M'C is to be added.
Now consider the case, when the ayana does not change, but the latitude also is north, like the
ayana, as in Fig. 2.
M¹
Fig. V. 2 C M
South ← S L → North
Now, clearly the Moon M at the end of M'M is bent downwards, with the result that M'C is deduc-
tive in this case, as the instruction says.
Let us next consider the case when the Moon's ayana is southward as in Fig. 3.
C M
M¹
Fig. V. 3 M C
South ← L S → North
Clearly in this case the Moon having north latitude is lifted up, and 'the result', CM', is additive,
and the Moon having south latitude is depressed, and CM' is subtractive. Thus we have, for ayana
and latitude having identical direction, 'the result' is subtractive and having different directions it
is additive. This is for visibility in the west.