1.1 Points, Lines and Planes Undefined Terms – Words/items that are only explained using examples or descriptions. Collinear – Points that lie on the same line. Coplanar – Points that lie on the same plane. Intersection – The set of points that two or more geometric figures have in common. Space – A boundless, three-dimensional set of all points. Can contain lines and planes. 1.2 Linear Measure Line Segment – A measurable part of a line that consists of two points, called endpoints, and all of the points between them. Congruent Segments – Segments that have the same measure. Constructions – A method of creating geometric figures without the benefit of measuring tools. Generally a compass and straightedge are used. Precision – A clustering of a group of measurements. Depends on the smallest unit of measure available on measuring tool. Accuracy – How close a measured value comes to the actual or desired value. 1.3 Distance and Midpoints Distance – The length of the segment between two points. Distance Formula Midpoint – The point halfway between the endpoints of a segment. Midpoint Formula Segment Bisector – Any segment, line, or plane that intersects a segment at its midpoint. 1.4 Angle Measure Ray – A part of a line that has one endpoint and extends indefinitely in one direction. Opposite Rays – Two rays on the same line that share a common endpoint. Angle – An object formed by two noncollinear rays that have a common endpoint. Sides – The rays that make up the angle. Vertex – The common endpoint of an angle. Degree – The unit used to measure angles. Equal to 1/360th of a turn around a circle. Angle Bisector – A ray that divides an angle into two congruent angles. 1.5 Angle Relationships Perpendicular – Lines, segments, or rays that form right angles. 1.6 Two Dimensional Figures Concave – If any of the lines that contain each side is extended and goes through the inside. Convex – If none of the lines that contain each side is extended and never pass through the interior. Names of Polygons Number of Sides 3 4 5 6 7 8 9 10 12 N Type (Name) of Polygon Triangle Quadrilateral Pentagon Hexagon Heptagon Octagon Nonagon Decagon Dodecagon n-gon Equilateral, Equiangular, and Regular Equilateral – All sides are equal. Equiangular – All angles are equal. Regular – All sides and angles are equal. It would be both Equilateral and Equiangular. Perimeter – The sum of the lengths of the sides of a polygon. Circumference – The distance around a circle. Area – The number of square units needed to cover a surface. 1.7 Three-Dimensional Figures Polyhedron – A solid with all flat surfaces that enclose a single region of space. Face – The polygons that make up the flat surface. Edge – The line segments where the faces intersect. Vertices – The point where three or more edges intersect. Regular Polyhedron – A polyhedron with all faces being regular congruent polygons. Surface Area – A two-dimensional measurement of the surface of a solid figure. Volume – The measure of the amount of space enclosed by a solid figure.