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
A Plane Is Born training at Staverton Airport in Gloucestershire with instructor Carl Bowen. - Building Begins Mark learns that before he starts to build his aeroplane he must attend a workshop on composite building techniques. His crash course is instructed by expert Neville Eyre. In part 2, back at the workshop, he begins work on his kit plane, starting with the Rudder. Some respite from plastics is provided at Gloucester airport where his flying training continues apace. In a regular feature, Dudley Pattison shows us the Isaac's Fury biplane he took fifteen years to build. - Wings Filming in the workshop, work begins