Elements of mechanics: treated by means of the differential and integral calculus (1887)
Peck, William G[uy], 1820-1892. [from old catalog] · New York, Chicago, A. S. Barnes & company · leaf 36
.) The angle a is estimated from the direction of positiveabscissas around to the left through 360°. For all values of a from 0° to 90°, and from 270° to 360°,the cosine of a will be positive, and, consequently, the com-ponent AL will be positive; that is, it will act in the directionof positive… … Fig. 10. 180°, we shall have For all values of a from 0° to 180°, the sine of a will bepositive, and the component AM willbe positive; that is, it will act in thedirection of positive ordinates. For allvalues of a from 180° to 360°, the sineof a will be negative, and the compo-nent AM will act in…
Mechanics
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