T H E E L E M E N T S |
Book VI Proposition 17 | |
But, if four straight lines be proportional, the rectangle contained by the extremes is equal to the rectangle contained by the means. [VI.16] Therefore the rectangle A, C, is equal to the rectangle B, D. But the rectangle B, D is the square on B, for B is equal to D; therefore the rectangle contained by A, C, is equal to the square on B. |
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