[...with the a]id of the third of this, take the midpoint between a and m upon the line n m, and open the compass to the space a d, and make the semicircle n b m upon the centre d; and where that circle touches the indefinite line m g at the point n, there cut the breadth of the said long rectangle between n c, which n c you will place at c o, and form your rectangle c o f m according to the breadth found.

7th

a b - c g - f c d n

Let the square be narrowed into the space of a given breadth, and then let the length to which it stretches be sought. Let the square a b c d be narrowed into the space e c, and then let the length to which it stretches be found, which you will do thus. Place the given breadth e c upon c f. Then draw the indefinite line f n along the side of the square c d. Then, by the fourth of this, set the line a d equal to the line f d, and open the compass to a d, and make the semicircle f a n, and where it cuts at n, there the length of the rectangle ends.