The Elements of Plane Geometry

AB>AC AB² ABCD AD² altitude angle AOB angle BAC angle equal angular points base BC bisector bisects the angle circle ABC circle cutting circles intersect circumcentre circumcircle common tangent cutting the circle cyclic quadrilateral describe a circle diameter divided drawn parallel drawn perpendicular equal and parallel equilateral triangle excircles EXERCISES exterior angle find the length given angle given circle given point given straight line given triangle incentre incircle isosceles triangle Let ABC median meets BC MISC opposite sides orthocentre parallel straight lines parallel to BC parallelogram parallelogram ABCD pedal triangle perpendicular to BC polygon PROP quadrilateral ABCD radius rectangle contained respectively rhombus right angles segments show that AC show that rect side BC Simson lines tangent theorem triangle ABC triangle right-angled twice rect vertex