| A | B |
|---|
| Acute Angle | an angle whose measure is between 0° and 90°. |
| Acute Triangle | a triangle with an angle having a measure less than 90°. |
| Adjacent Angles | angles with a common side and a common vertex but no common interior points. |
| Adjacent Arcs | are arcs on the same circle and have exactly one point in common. |
| Alternate Interior Angles | interior angles on diagonally opposite sides of the transversal. |
| Altitude of a Triangle | a line segment extending from any vertex that is perpendicular to the line containing the side opposite the vertex. |
| Angle | two rays sharing a common endpoint. |
| Angle Bisector | a ray or line segment that splits an angle into two equal halves. |
| Apothem | the apothem of a regular polygon is the length of the perpendicular line segment from the center to a side |
| Arc | part of a circle. |
| Arc Length | is the product of the ratio of and the circumference of the circle the arc is part of. |
| Area | the area of a plane figure is the number of square units enclosed by the figure. |
| Axiom | a statement accepted without proof. |
| Bisect | to cut into equal parts. |
| Bisector | a line |
| Central Angle of a Circle | an angle whose vertex is the center of the circle. |
| Central Angle of a Regular Polygon | is the angle formed by two consecutive radii taken from the vertices of the polygon. |
| Centroid | the intersection point of the three medians of a triangle |
| Chord | any line segment whose endpoints are points on the circle. |
| Circle | a set of all points if a plane equidistant from a center point. |
| Circumcenter | the intersection point of the three perpendicular bisectors of a triangle. |
| Circumference | the distance around a circle. |
| Circumscribe | (1) a circle is circumscribed around a polygon if the vertices of the polygon are on the circle. |
| Collinear | being on the same line. |
| Complementary | two angles are complementary if the sum of their measures is 90°. |
| Compositon of Transformations | a composition of two transformations is a transformation in which the second transformation is performed on the range of the first. |
| Concave Polygon | a polygon where at least one interior angle is greater than 180°. |
| Concentric Circles | circles that lie in the same plane and have the same center. |
| Concurrrent | concurrent linse are three or more lines that meet at one point. |
| Conditional | an if ... then ... statement. |
| Cone | a pyramid whose base is a circle. |
| Congruent | having the same length or shape. |
| Congruent Arcs | two arcs that have the same measure and are in the same circle or congruent circles. |
| Congruent Circles | circles with congruent radii. |
| Congruent Polygons | polygons whose corresponding sides and corresponding angles are congruent. |
| Congruent Segments | segments having the same length. |
| Conjecture | a conclusion reached by using inductive reasoning. |
| Consecutive Angles | in a polygon |
| Construction | using only a straight edge and a compass to draw a geometric figure. |
| Contrapositive | the contrapositive of if p then q is if not q then not p. |
| Converse | the converse of if p then q is if q then p. |
| Convex Polygon | a polygon where each interior angle is less than or equal to 180°. |
| Coordinates | (1) of a point on a number line: the distance and direction from the origin; |
| (2) of a point in a coordinate plane: a set of numbers in the form (x | y). |
| Coordinate Plane | the plane formed by the perpendicular intersection of two number lines at their origins. |
| Coplanar | being on the same plane. |
| Corollary | a statement that can be proven directly using the theorem it is associated with. |
| Corresponding Angles | angles that have the same relative position. |
| Counter Example | a particular example or instance that demonstrates that a statement is not true. |
| Cube | a prism with all square faces. |
| Cylinder | a prism whose bases are congruent circles. |
| Decagon | a ten sided polygon. |
| Deductive Reasoning | the process of reasoning logically from given facts to a necessary conclusion. |
| Diagonal | a line segment connecting two non-consecutive vertices. |
| Diameter | a chord passing through the circle's center. |
| Dilation | a dilation or similarity transformation |
| (1) if n>1 | the dilation is an enlargement |
| (2) if 0<n<1 | the dilation is a reduction. |
| Distance from a point to a line | is the length of the perpendicular line segment from the point to the line. |
| Dodecagon | a twelve sided polygon. |
| Dodecahedron | a twelve faced polyhedron. |
| Edge | the intersection of the faces of a polyhedron. |
| Equiangular Triangle (or Polygon) | a triangle or polygon whose angles are all congruent. |
| Equidistant | being of equal distance from two designated points. |
| Equilateral Triangle | a triangle with three congruent sides. |
| Euclidean Geometry | geometry of the plane in which Euclid's Parallel Postulate (there is exactly one line parallel to line l through point p) is true. |
| Exterior Angle of a Polygon | an angle formed by a side and an extension of an adjacent side of a polygon. |
| Face | one of the bounding polygons of a polyhedron. |
| Foundation Drawing | shows the base of a structure and the heigth of each part. |
| Friez Pattern | a pattern that repeats itself along a straight line. |
| Geometric Mean | the geometric mean of two positive numbers a and b is the the positive number x such that |
| Glide Reflection | a composition of three reflections in lines that intersect in more than one point. Equivalently |
| Glide Reflection Symmetry | a repeating pattern has glide reflection symmetery if it can be mapped onto itself by a glide reflection. |
| Golden Ratio | is the ratio of the length of a golden rectangle and its width. The value of the golden ration is |
| Golden Rectangle | a rectangle that can be divided into a square and a rectangle that is similar to the original rectangle. |
| Great Circle | the intersection of a sphere and a plane containing the center of the sphere. A great circle di |
| Hemisphere | half a sphere. |
| Heptagon | a seven sided polygon. |
| Heptahedron | a seven faced polyhedron. |
| Heron's Formula | a formula for finding the area of a triangle given the length of its sides. |
| Hexagon | a six sided polygon. |
| Hexahedron | a six faced polyhedron |
| Hypotenuse | the side opposite the right angle in a right triangle. |
| Icosahedron | a twenty faced polyhedron. |
| Identity | an equation that is true for all allowed values of the variable. |
| Image | the result of having performed a transformation upon a pre-image. |
| Incenter | the intersection point of the three angle bisectors of a triangle. |
| Indirect Measurement | used to measure things that are difficult to measure directly. (Right Triangle Similarity) |
| Indirect Reasoning | all possibilities are considered and then all but one are proved false. |
| Inductive Reasoning | reaching a conclusion based upon a pattern of specific examples or past events. |
| Initial Point | the starting point for a vector. |
| Inscribe | (1) a circle is inscribed in a polygon if all the sides of the polygon are tangent to the circle |
| Inscribed Angle | an angle inside a circle whose vertex is on the circle. |
| Intercepted Angle | an angle formed by two secants intersecting outside a circle. |
| Intercepted Arc | an arc whose endpoints are on the sides of the inscribed angle and where remaing points lie in the interior of the angle. |
| Intersection | the set of points that two geometric figures have in common. (where the two figures meet or cross) |
| Inverse | the inverse of the statement if p then p is if not p then not q. |
| Isometric Drawing | a drawing of a three dimensional figure/object that shows a corner view of the figure. |
| Isometry | a transformation in which the original figure and its image are congruent. |
| Isosceles Trapezoid | a trapezoid whose non-parallel sides are congruent. |
| Isosceles Triangle | a triangle with at least two congruent sides. |
| Lateral Area | the sum of the areas of a pyramid or prisim's lateral faces. |
| Lateral Face | prisim: the parallelograms connecting the bases of the figure; |
| Line | a set of points that extends infinitely in opposite directions. |
| Line Segment | consists of two distinct points (endpoints) and all the points between them. |
| Length | the distance between two points. |
| Locus | a set of points that meet a stated condition. |
| Major Arc | an arc with measure greater than 180° |
| Measure of an Arc | the measure of a minor arc is equal to the measure of its central angle. |
| Median of a Trapezoid | the line segment connecting the midpoints of the non-parallel sides of a trapezoid. |
| Median of a Triangle | a line segment that joins any vertex of a triangle to the midpoint of the side opposite that vertex. |
| Midpoint | the middle point that divides a line into two equal line segments. |
| Midsegment | of a trapezoid: the line segment that joins the endpoints of the non-parallel sides of a trapezoid.. |
| Minor Arc | an arc with measure less th |
| Net | a two dimensional pattern that can be folded into a three dimensional figure. |
| N-gon | an n sided polygon. |
| Nonagon | a nine sided polygon |
| Obtuse Triangle | a triangle with an angle having a measure more than 90° but less than 180°. |
| Octogon | an eight sided polygon. |
| Octahedron | an eight faced polyhedron. |
| Opposite Rays | collinar rays with the same endpoint. |
| Orientation | same: a reflection is not needed to map on figure onto the other. |
| Orthocenter | the intersection of the three altitudes of a triangle. |
| Orthographic drawing | a drawing that shows the top |
| Parallel | two coplanar lines that do not intersect. |
| Parallelogram | a quadrilateral with two pairs of parallel sides. |
| Parallel Planes | planes that do not intersect. |
| Pentagon | a five sided polygon |
| Pentahedron | a five faced polyhedron. |
| Perimeter of a Polygon | the sum of the lengths of the sides of a polygon. |
| Perpendicular | two lines |
| Perpendicular Bisector | a line segment or ray that is perpendicular to a segment at its midpoint. |
| Perspective Drawing | a way of drawing objects on a flat surface so that they look to same as they appear to the eye. One point perspective has one vanishing point |
| Plane | a flat surface that extends infinitely in all directions. |
| Point | a location in space with neither length nor width. |
| Point Symmetry | a figure with rotational symmetry of 180°. |
| Polygon | a figure with three or more coplanar points joined by line segments such that |
| Polyhedron | a solid figure bounded by plane polygons. |
| Polyomino | a plane figure formed by joining unit squares along their edges. |
| Postulate | a statement accepted without proof. |
| Prism | a geometric figure that has two bases that are congruent polygons lying in parallel planes. |
| Proportion | a statement that two ratios are equal. |
| Pyramid | a three dimensional figure having as a base one polygon and whos sides (lateral faces) meet at a point above the base's plane. |
| Pythagorean Triple | a set of three integers that satisfy the Pythagorean Theorem. |
| Quadrilateral | any four sided figure |
| Radius | a line segment whose endpoints are the center of the circle and a point on the circle. |
| Radius of a Regular Polygon | the distance from the center of the polygon to one of the veritces. |
| Ray | part of a line that starts at one endpoint and extends infinitely in one direction. |
| Reduction | a dilation or similarity transformation |
| Reflection | a reflection in line r is a transformation such that if a point A is on line r |
| Reflection Symmetry | a figure has reflection symmetry if there is a reflection that maps the figure to itself. |
| Regular Polygon | a polygon where all the sides are congruent and all the angles are congruent. |
| Remote Interior Angles | for each exterior angle of a triangle |
| Resultant | the sum of two vectors. |
| Rhombus | a quadrilateral with four congruent sides. |
| Right Angle | an angle whose measure is 90°. |
| Right Triangle | a triangle with a 90° angles. |
| Rotation | a rotation of x° around (about) a point R is a transformation such that for any point V |
| Rotational Symmetry | if there is a rotation of 180° or less that maps the figure onto itself. |
| Same Side Interior Angles | interior angles that lie on the same side of a transversal. |
| Scale Drawing | in a drawing where the scale compares the length of each segment in the drawing to the actual length being represented. |
| Scale Factor | in a dilation |
| Scalene Triangle | a triangle with no congruent sides. |
| Secant | any line that contains a chord. |
| Sector of a Circle | the region bounded by two radii and their intercepted arc. |
| Segment | part of a line consisting of two endpoints and all the points between them. |
| Segment Bisector | a line |
| Segment of a Circle | the partof a circle bounded by an arc and the segment joining its endpoints. |
| Semicircle | an arc with measure = 180° . |
| Similar Polygons | polygons whose corresponding angles are congruent and corresponding sides are proportional. |
| Similar Solids | solids with the same shape and corresponding dimensions are proportional. |
| Similarity Ratio | the ratio of the lengths of corresponding sides of similar polygons or solids. |
| Skew | lines are skew if they do not lie in the same plane. |
| Slope | the measure of the steepness of a line. |
| Space | the set of all points. |
| Sphere | the set of all points in space equidistant from a center point. |
| Spherical Geometery | where a plane is considered to the the surface of a sphere and a line is considered to be a great circle of the sphere. |
| Spherical Parallel Postulate | Through a pont not on a given line |
| Square | a quadrilateral with four right angles and four congruent sides. |
| Straight Angle | an angle whose measure is 180°. |
| Supplementary | two angles are supplementary if the sum of their measures is 180°. |
| Surface Area | of a prisim |
| Symmetry | a figure has symmetry if there is an isometry that maps the figure onto itself. |
| Tangent | a line in the same plane as the circle intersecting the circle at exactly one point. |
| Tessellation | a repeating pattern of figures that completely covers a plane without gaps or overlaps. |
| Tessellation | Pure |
| Tetrahedron | a polyhedron with four faces. |
| Theorem | a statement that has been proven using postulates |
| Transformation | a change in the position |
| Translation | a transformation that moves points the same distance and in the same direction described by a vector. |
| Translational Symmetry | in a repeating pattern |
| Transversal | a line that cuts across two or more coplanar lines. |
| Trapezoid | a quadrilateral with two parallel sides and two non-parallel sides. |
| Triangle | three non-collinear points connected consecutively by three line segments |
| Vector | any quantity that has magnitude and direction. |
| Vertex | the common endpoints shared by the rays of an angle. |
| Vertical Angles | two non-adjacent angles formed by the intersection of two lines. |
| Volume | a measure of the space a figure occupies. |
