These latter are nothing more or less than clumsy lugs or quadrilaterals.
Thus, in the circle and the quadrilateral (the parts are not circles or quadrilaterals).
And let all quadrilaterals other than these be called trapezia.
Then the two circles, the four triangles, and the three quadrilaterals respectively are similar figures.
That two quadrilaterals having an equal base and equal altitude are equivalent.