T H E E L E M E N T S |
Book II Proposition 9 | |
But the squares on AD, DF are equal to the square on AF, for the angle at D is right; [I.47] therefore the squares on AD, DF are double of the squares on AC, CD. And DF is equal to DB; therefore the squares on AD, DB are double of the squares on AC, CD. Being what it was required to prove. |
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