Mechanical drawing. Elementary and advanced (1910)
Reid, John S. (John Simpson), 1856- · New York, J. Wiley & sons; [etc, etc.] · leaf 47
A B D Fig. 50. F Fig. 51. Fi2.b* ii! To Find a Fourth Proportional to threeGiven Right Lines AB, CD, and EF.— Make ^^=thegiven line AB. Draw GI = CD, making any convenientangle to GH. Join HI. From G lay off GK = EF. FromK draw a parallel to HI cutting GI in L. GL is the fourthproportional required.
