The First Book of Euclid's Elements: Arranged for Beginners

ABC is equal ABCD adjacent angle ABC angle ACB angle BAC angle equal applied base base BC called centre circle coincide Consider the triangles Construction crosses describe diagonal difference direction distance draw equal in area equal respectively equal to BC equidistant equilateral triangle exterior angle fall figure finite straight line four geometrical given angle given finite straight given point given straight line greater half included angle indicate interior opposite angle intersect isosceles triangle length less Let ABC line joining lines drawn meet middle point opposite sides pair parallel parallelogram perpendicular plane portion position produced Proof Prop Proposition Q.E.D. EXAMPLES quadrilateral Question radius represent required to prove right angles Shew side BC sides equal solid square straight angle surface taken triangle ABC triangles are equal turning Wherefore