b – c c – o – 4 2 1 – c c - a
a is worth b, and is worth c filled up with the whole square.

Of portions with an equal chord, that one will have the greater capacity which has the longer sagitta, that is, the more curved arc.

* All triangular surfaces, rectilinear and curvilinear, of whatever length or height, with uniformly non-uniform sides, made upon the same base, are equal to one another.

e d a - c b

All triangular figures, uniformly non-uniform, whether curvilinear or rectilinear, made between parallel lines, are always equal to one another. It is proved: because the helix is equal to the triangle a b c, and the triangle b c d and the triangle b c e are also equal to the triangle a b c; and since, when several things are equal to a third, they are also equal to one another, it follows that the helix, being equal to the triangle a b c – and the other 2 triangles being equal to the same triangle a b c – they are also equal to one another.

The proportion that holds from one whole to a similar whole holds also from part to similar part; and because the circumferential line makes a space parallel to itself about the center of the circle, whence the semidiameter is like the rectilinear parallel space, whatever is done in the rectilinear parallel is understood to be done in the curvilinear parallel space.

1 - 1/8; 2 - 2/8; 3 - 3/8; 4 - 4/8; 5 - 5/8; 6 - 6/8; 7 - 7/8; 8 – a 8/8

portion a is one.

The seventh of the next-to-last, divided into 7, is worth the eighth of the last, divided into 8.

40

5 times 8

35

Take 2 numbers such that 1/7 of the smaller is worth as much as the eighth of the greater. Take 8 and 7, and you will find that the unit of which 8 is composed is worth as much as the unit of which 7 is composed. Therefore, of the 2 circles, one being 7/8 of the other, the unit taken from 8 is worth the unit taken from 7.