The Thirteen Books of Euclid's Elements

angle ABC angle BAC apotome axis base BC is equal bisected centre of gravity circle ABCD circumference commensurable in length commensurable in square cone continued proportion cube cylinder diameter drawn parallel ellipse equal angles equiangular equimultiples Eucl frustum given straight line gnomon greater hyperbola incommensurable inscribed less Let ABC let the straight magnitudes medial straight line meet multiplying opposite sections parabola parallelogram perpendicular plane plane of reference point of contact polygon prime prism produced PROPOSITION 14 proved pyramid Q. E. D. PROPOSITION ratio rational straight line rect rectangle contained remaining angle right angles segment side similar Similarly solid sphere square number squares on AC straight line AB straight line AC straight lines commensurable surface tangent trgl triangle ABC twice the rectangle vertex