Essentials of Geometry (plane).

AB² AC and BC AC² AD² adjacent angles altitude angles are equal apothem approach the limit arc BC base and altitude BC² bisector bisects centre chord circumference circumscribed construct the triangle Converse of Prop decagon diagonals diameter Draw line EFGH equal angles equal respectively equally distant equiangular polygon equilateral triangle equivalent exterior angle figure Given line given point given square homologous sides hypotenuse isosceles triangle line joining measured by arc middle point non-parallel sides number of sides opposite sides parallel parallelogram perimeter perpendicular points of sides polygons AC produced Prove Proof quadrilateral radii radius ratio rectangle regular inscribed regular polygon rhombus right angles right triangle secant segment side BC similar triangles subtended tangent THEOREM transversal trapezoid triangle ABC triangle is equal vertex vertices