Preston, Thomas, Joly, Charles Jasper, 1864-1906, Parsons, John Herbert, Sir, 1868-1957, donor, University College, London. Library Services · London : Macmillan and Co. · leaf 70
n a.,), = A sin {wt - a), if A cos a =: cos ttj^ + cos a2 and A sin a = sin + sin a^. Therefore by squaring and adding we find A'-^ = cti' + + 2a-^a2 cos (a^ - a.-^, and by division ^ sin ttj + a.2 sin a.2 tan a = — • a-^ cos ttj + a.2 cos ag ^ Fresnel, (Euvres completes, torn. i. pp. 288-293 ;… … other words, the motion of R is the resultant of the motions of P and Q superposed. Now R executes a simple harmonic vibration of amplitude OC and phase XOC — that is, if the amplitudes of the vibrations of P and Q be repre- sented by the lines OA and OB, while the phases of the same vibrations are…
![An illustration from The theory of light [electronic resource], 1901, leaf 70](https://img.insideoutlibrary.com/img/1024/ia-b21286462-70-0.webp)
