Light, photometry and illumination : a thoroughly rev. ed. of ''Electrical illuminating engineering'' (1912)
Barrows, William Edward, 1878-1960 · New York ; London : McGraw-Hill Book Co. · leaf 164
re as follows: Table 25 Cosine Values for Constructing the Rousseau Diagram Degrees... 0 10 20 30 40 50 60 70 80 90 Cosine 1.0 .985 .939 .866 .766 .643 .500 .342 .173 0 If, on the horizontal lines drawn from the terminals of the suc-cessive altitudes, we lay off to scale the values of the… … Fig. 85.—Construction of Rosseau diagram. value of the source of light and the proportional jDart of the totallight in any zone will be clearly shown. The value of this areain terms of the product of the scales to which the curve wasplotted divided by the sum of the ordinates or altitudes will…
Light · Photometry · Electric lighting
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