Squaring of figures and transformation of quadrilaterals
Lunes, area transformation and Euclid, dated Amboise, 24 June 1518
A dense geometrical sheet on the squaring and transformation of plane figures: curvilinear triangles (lunes) are equated to circles and to squares, and a rule stretches a quadrilateral into a longer one of equal area and then restores it, a proof declared acceptable among mathematicians. It cites Euclid, the 43rd proposition of Book I of the Elements, and states that the squares on the sides of a right angle in a semicircle are always equal in value. A dated heading records the 24th of June, the day of St John, 1518, at Amboise in the palace of Cloux, and a small marginal plan is labelled Rooms of the lions of Florence. Several further figures carry only letter-labels.
On this page
Curvilinear triangles equal to circles and squares
The curvilinear triangles a b and d are worth the circles c f and also half the greatest circle. Removing the a d portions and the four greatest portions of each circle leaves two squares equal to the b and the triangles.
Stretching a quadrilateral and restoring it
Let a be the given quadrilateral and b the length to which it is to be extended; adding b to the lower side and drawing the touching line h n makes a surface S equal to a, since n d multiplied by g h equals L p multiplied by r K. The elongated parallelogram then shortens back into the original square without any change of quantity.
Squares on the sides of a right triangle
The right-angled triangle a is worth each of the other triangles, and the square f g h i is worth the other two squares d b c e together. The figure sets out the equality of the square on the hypotenuse with those on the legs of an isosceles right triangle.
Right angles inscribed in a semicircle
The sides of the right angles made in a semicircle are always of equal value in the squares created by their multiplications. Four right angles are drawn within the semicircle to demonstrate the relation.
Dated heading: Amboise, 24 June 1518
On the 24th of June, the day of St John, 1518, at Amboise in the palace of Cloux. Leonardo then states his plan to extend the given quadrilaterals according to their lengths and give the due reductions of their widths.
Marginal plan: Rooms of the lions of Florence
A small building plan near the margin is labelled Rooms of the lions of Florence. It stands apart from the surrounding geometry as a jotted architectural note.
