Bīrūnī, Muḥammad ibn Aḥmad, Alberuni's India (v. 2)

(London :  Kegan Paul, Trench, Trübner & Co.,  1910.)



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74                          ALBERUNTS INDIA.

of its orbit, which is found in the computations of the
corrections of sun and moon. AB is the diameter of
the body of the sun, CD is the diameter of the earth,
ODH is the cone of the shadow, HL is its elevation.
Further, draw CE parallel to DB. Then is AE the
difference between AB and OD, and the normal line
CT is the middle distance of the sun, i.e. the radius of
its orbit derived from the yojctnas of heaven (v. p. 72).
From this the true distance of the sun always differs,
sometimes being larger, sometimes smaller. We draw
CK, which is of course determined by the parts of the
sine. It stands in the same relation to CT, this being
the sinus totits ( = radius), as the yojctnas of CK to the
yojanas of OT. Hereby the measure of the diameter is
reduced to yojanas.

The yojanas of AB stand in the same relation to the

yojancts of TO as the minutes of AB to the minutes

of TO, the latter being the sinus totits.    Thereby AB

becomes known and determined by the minutes of the

sphere, because the sinus totus is determined by the

Quotations   measuro of the circumference.    For this reason Pulisa

Brahma- '' says : " Multiply the yojctncts of the radius of the sphere

Baiabiiadra. of  the   sun  ov the moon by the true distance, and

divide the product by the sinus totits.    By the quotient

you get for the sun, divide   22,278,240,  and  by the

quotient you get for the moon, divide 1,650,240.    The

quotient then represents the minutes of the diameter of

the body of either sun or moon."

The last-mentioned two numbers are products of the
multiplication of the yojanas of the diameters of sun
and moon by 3438, which is the number of the minutes
of the sinits totits.

Likewise Brahmagupta says : " Multiply the yojanas
of sun or moon by 3416, i.e. the minutes of the sinus
totus, and divide the product by the yojctnas of the
radius of the sphere of sun or moon." But the latter
rule of division is not correct, because, according to it.
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