Geometry Definitions textbook tutorials - definitions - constructions - postulates and theorems - internet activities and resources mathematical logic symmetry and similarity points, lines and planes angles parallel lines triangles quadrilaterals polygons circles 3-Dimensional Geometry conclusion angle of rotation between acute angle alternate interior angles acute triangle consecutive angles decagon center base conditional statement contraction colinear angle  alternate exterior angles altitude of a triangle consecutive sides exterior angle circle cylinder congruent dilation congruent segments angle bisector  corresponding angles base of a triangle opposite angles hexagon circumscribed angle equation of a plane conjecture image coplanar angle measure consecutive interior angles  height opposite sides interior angle concentric circles lateral surface area contrapositive line of symmetry intersect complementary linear pair hypotenuse kite nonagon diameter parallel to a plane converse   midpoint congruent angles same side interior angles legs parallelogram octagon inscribed angle prism counterexample reflection line linear pair  same side exterior angles  median of a triangle quadrilateral pentagon radius pyramid definition rotation parallel obtuse angle transversal  incenter of a triangle rectangle regular polygon tangent sphere deductive reasoning similar polygons perpendicular right angle vertical angles obtuse triangle rhombus     surface area hypothesis transformation perpendicular bisector side of an angle   right triangle square     volume inductive reasoning translation plane supplementary   sides trapezoid      xy plane inverse   point vertex of an angle   vertex (verticies)        xz plane postulate   segment bisector vertical angles            yz plane Reflexive Property   skew               Symmetric Property                   Transitive Property                   theorem                   undefined term