Or thus: An Oblong is a rectangled parallelogramme, being not equilater: H. As here is ae, io.
This second kinde of rectangle is of Euclide in his elements properly named for a definitions sake onely.
The rate of Oblongs is very copious, out of a threefold section of a right line given, sometime rationall and expresable by a number: The first section is as you please, that is, into two segments, equall or unequall: From whence a five-fold rate ariseth.
2 An oblong made of an whole line given, and of one segment of the same, is equall to a rectangle made of both the segments, and the square of the said segment. 3. p ij.
It is a consectary out of the [7 e xj]. For the rectangle of the segments, and the quadrate, are made of one side, and of the segments of the other.
As let the right line ae, be 6. And let it be cut into two parts ai, 2. and ie, 4. The rectangle 12. made of ae, 6. the whole, and of ai, 2. the one segment, shall be equall to iu, 8. the rectangle made
of the same ai, 2. and of ie, 4. And also to ao, 4. the quadrate of the said segment ai, 2.
Now a rectangle is here therefore proposed, because it may be also a quadrate, to wit, if the line be cut into to equall parts.
Secondarily,