(23)IV. EX D & L in O duc rectas: erit an-gulus DOL=ABC.DEMONST. In triangulis ACC &DOL ex constr. sunt omnia latera mu-tuò æqualia: ergo O=B(35) q. e. d.92. COROL. Hinc ducitur modusfacilior rectae AB per datum punctumO ducendi parallelam OL: nam ductârectâ BO fiat angulus O=B (91) &erit crus OL cruri AB parallelum (82)93. SCHOL. Faciliùs in charta rectaeBE parallela CD per datum punctum Oducitur ope regulae AB, & cujusvis trian-guli ex solida materia confecti ACO.Nempe rectæ BE applico trianguli latusCO: lateri AC apprimo regulam AB:tum regulâ immotâ promoveo triangulum(ità tamen, ut latus AC semper regulaecongruat) donec latus CO tranſeat per da-tum punctum O: ducta CD erit rectae BEparablela. Nam angulus ACO=ACD, &ACO=ABE(15) proinde ACD=ABE(51) itaque CD & BE sunt parallelae (88)94. DEF. Semicirculus AlB ex ma-teria solida coniectus, cujus circumferentia in 180 gr. divisa est, vocatur Trans-portator.95. PROBL. Angulum DCE in char-ta descriptum metiri.SOLU TIO.I. Vertici Cimpone trans-portatoris centrum C, ità, ut diameterAB incumbat cruri DC. II. Nota pun-ctumB 3

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