Vector Addition Given Resultant
Illustration "where ad is the given resultant, if the two components have the magnitudes represented by ac and ab, the directions ac and ab would solve the problem, or the direction ac1 and ab1 would equally well fulfil (sic) the conditions."
Peter Schwamb, S.B. And Allyne L. Merrill, S.B. Elements Of Mechanism (New York: John Wiley & Sons, Inc., 1905) 8
Courtesy the private collection of Roy Winkelman