IF three straight lines be proportionals, the rectangle contained by the extremes is equal to the square of the mean ; and if the rectangle contained by the extremes be equal to the square of the mean, the three straight lines are proportionals. The Elements of geometry [Euclid book 1-3] in general terms, with notes &c ... - Pàgina 26 per Euclides - 1821 Visualització completa -
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