Elementary Synthetic Geometry of the Point, Line and Circle in the Plane

ABCD Algebra altitude base becomes called centre centre-line chord circle coincide collinear common concurrent congruent considered constant construct Converse corresponding cuts denote describe determine diagonals diameter difference direction distance divided draw drawn equal equilateral expressed external figure fixed point four geometric given given line given point gives greater harmonic Hence internal intersect inverse joins length lies line-segment mean measure median meet middle point opposite sides orthogonally pair parallel passes pencil perpendicular perspective placed plane polar polygon position Proof proportional proved quadrangle radical axis radius range ratio reciprocal rectangle regular relation respect right angle right bisector rotation segment sides similar Similarly similitude square straight symbol taken tangent theorem touch triangle vertex vertices