Tangential quadrilateral all of whose sides are tangent to a single conic section has three diagonals that meet at a point. From a tangential quadrilateral, one can form a hexagon with two 180° angles, by placing two new vertices at two opposite points of tangency; all six of the sides of this hexagon lie on lines tangent to the inscribed circle, so its diagonals meet at a point. But two of these diagonals are the same as the diagonals of the tangential quadrilateral, and the third diagonal of the hexagon is the line through two opposite points of tangency. Repeating this same
Rebate plane Rebate plane The rebate plane (also known as the rabbet plane) is a hand plane designed for cutting rabbets in wood. It's a simple tool used in many Western countries with hundreds of years of history. It was in use in England at least as early as the 11th century. The rebate plane is one of a group of planes, including the shoulder plane, bullnose plane and carriage makers plane, in which the blade protrudes by a very small amount - usually less than half a millimetre - from the sides of the plane body on both sides. The blade