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
Shoulder plane for joinery. Unlike the rebate plane, the shoulder plane is intended to cut end grain. There are therefore differences between it and a rebate plane in the angles at which the iron (blade) is set. A shoulder plane also has a much finer set mouth, which allows finer shavings to be taken. Shoulder plane The shoulder plane (also bullnose plane) is a plane tool with a blade flush with the edges of the plane, allowing trimming right up to the edge of a workpiece. Like a rebate plane, the shoulder plane's blade extends, therefore cuts, to the full width of