The fifth is thus: The angle of the greater section eai, is greater than a right angle: because it containeth a right-angle.
The sixth is thus, the angle aoe, in a lesser section, is greater than a right angle, by the [14 e xvj]. Because that which is in the opposite section, is lesser than a right angle.
The seventh is thus. The angle eao, is lesser than a right-angle: Because it is part of a right angle, to wit of the outter angle, if ia, be drawne out at length.
And thus much of the angles of a circle, of all which the most effectuall and of greater power and use is the angle in a semicircle, and therefore it is not without cause so often mentioned of Aristotle. This Geometry therefore of Aristotle, let us somewhat more fully open and declare. For from hence doe arise many things.
Therefore
22 If two right lines jointly bounded with the diameter of a circle, be jointly bounded in the periphery, they doe make a right angle.
Or thus; If two right lines, having the same termes with the diameter, be joyned together in one point, of the circomference, they make a right angle. H.
This corollary is drawne out of the first part of the former Element, where it was said, that an angle in a semicircle is a right angle.
And