T H E E L E M E N T S |
Book I Proposition 46 | |
And, since the straight line AD falls upon the parellels AB, DE, the angles BAD, ADE are equal to two right angles. [I.29] But the angle BAD is right; therefore the angle ADE is also right. And in parallelogramic areas the opposite sides and angles are equal to one another [I.34]; therefore each of the opposite angles ABE, BED is also right. |
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