Astronomy, a handy manual for students and others (1918)
Dyson, Frank Watson, Sir, 1868-1939 · New York, E.P. Dutton & Co. · leaf 39
lled a right-angle. If thisangle is divided into 90 equal parts, each is called one degree, andwritten i°. One-sixtieth part of a degree is called a minute, andwritten 1. One-sixtieth part of a minute is called a second,and written 1. 28 ASTRONOMY the angles between the directions of the Moon,… … Diag. XV. is as compared with OA or OB, the radius of theEarth. In actual practice trigonometrical calcula-tions are used, but that is only because drawing toscale cannot be done with sufficient accuracy. The Moons distance was thus satisfactorily deter-mined, and Ptolemy tried to use his result in…
Astronomy
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