2 And in any parallelogrammic area let any one whatever of the parallelograms about its diameter with the two complements be called a gnomon.
IN omni parallelogrammo spatio, vnumquodlibet eorum, quæ circa diametrum illius sunt, parallelogrammorum, cum duobus complementis, Gnomon vocetur.
第二界
諸方形、有對角線者。其兩餘方形。任偕一角線方形。為罄折形。(p. 八四)
甲乙丙丁、方形。任直、斜角。作甲丙對角線。從庚點作戊己、辛壬、兩線。與方形邊平行。而分本形為四方形。其辛己、庚乙、兩形為餘方形。辛戊、己壬、兩形為角線方形。一卷界 \\ 說三六兩餘方形。任偕一角線方形。為罄折形。如辛己、庚乙、兩餘方形。偕己壬角線方形。同在癸子丑圜界內者。是癸子丑罄折形也。用辛戊角線方形、倣此。
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