e xv. Then if you doe omit the periphery in the middest betweene them both, as here uy, and shalt adde oies the remainder to each of them, the whole oiesy, subtended to the angle at u: And uoies, subtended to the angle at y, shall be equall. Therefore the angles in the periphery, insisting upon equall peripheries are equall.
Of the circumscript it is likewise true, if the circumscript be understood to be a circle. For the perpendiculars from the center a, unto the sides of the circumscript, by the [9 e xij], shal make triangles on each side equilaters, & equiangls, by drawing the semidiameters unto the corners, as in the same exāple.
2. It is equall to a triangle of equall base to the perimeter, but of heighth to the perpendicular from the center to the side.
As here is manifest, by the [8 e vij]. For there are in one triangle, three triangles of equall heighth.
The same will fall out in a Triangulate, as here in a quadrate: For here shal be made foure triangles of equall height.
Lastly every equilater rectilineall ascribed to a circle, shall be equall to a triangle, of base equall to the perimeter of the adscript. Because the perimeter conteineth the bases of the triangles, into the which the rectilineall is resolved.
3. Like rectilinealls inscribed into circles, are one to another as the quadrates of their diameters, 1 p. xij.
