Quadrilaterals Inscribed in Circles
Five figures of quadrilaterals set in circles, with notes on triangle and quadrilateral angles
Five circles are drawn down the sheet, each enclosing a quadrilateral crossed by its diagonals — figures of quadrilaterals inscribed in a circle. Two short geometric statements accompany them: that all the angles of a triangle are worth two right angles, and that all the opposite angles of the quadrilateral are equal. The studies belong to Leonardo's geometry of figures inscribed in the circle.
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Five quadrilaterals inscribed in a circle
A caption names five figures of quadrilaterals inscribed in the circle, matching the five circled quadrilaterals drawn with their diagonals down the right side of the leaf. They form a small series of cyclic-quadrilateral studies.
Angle relations of triangle and quadrilateral
Two theorems are noted: that all the angles of a triangle are worth two right angles, and that all the opposite angles of the quadrilateral are equal. They state the angular properties underlying the inscribed figures.