... proportion(4, 5 in the argument 3–7; 12 , 13 in the argument 10 15 ; 16 , 18 in the argument 15 19 ). In Steps 3–7, both ratios are substituted. In 10 15 and 15 19 , only one90on the sphere and the ... Elements V .18 . 19 3Interlude, recalling Elements XII .14 . 19 4Elements V.9. 19 5SC I .15 . 19 6Elements VI.4.88on the sphere and the cylinderiThe answer may be the following. Elements XII .1 states ... justifications(Steps 6, 11 , 14 , 17 ). Heiberg brackets all, and of course it is difficult to forma judgment. What must be said is that the nature of three of these justificationsis special: Steps 6, 11 and 17 all...