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Two rays sharing a common endpoint. Angles are typically measured in degrees or radians.
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An angle that has measure less than 90°.
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Two angles in a plane which share a common vertex and a common side but do not overlap. Angles 1 and 2 below are adjacent angles.
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The surface included within a closed figure, measured by the number of square units needed to cover the surface.
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A line segment, line, or plane that divides a geometric figure into two congruent halves.
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A complete circular arc. Circumference also means the distance around the the outside of a circle.
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Lying on the same line.
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Two acute angles that add up to 90°. For example, 40° and 50° are complementary In the diagram below, angles 1 and 2 are complementary.
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Intuitively speaking, curved away from the eye. A concave figure is a set of points some of whose chords include points that are in the set.When at least one of the interior angles of a polygon is greater than 180°, it is a concave polygon. The inside surface of a bowl is concave when viewed from above.
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Exactly equal in size and shape. Congruent sides or segments have the exact same length. Congruent angles have the exact same measure. For any set of congruent geometric figures, corresponding sides, angles, faces, etc. are congruent.
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convexpolygon A geometric figure with no indentations. Formally, a geometric figure is convex if every line segment connecting interior points is entirely contained within the figure's interior.
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On the coordinate plane, the pair of numbers giving the location of a point (ordered pair). In three-dimensional coordinates, the triple of numbers giving the location of a point (ordered triple). In n-dimensional space, a sequence of n numbers written in parentheses.
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cylinderA three-dimensional geometric figure with parallel congruent bases. The bases can be shaped like any closed plane figure (not necessarily a circle) and must be oriented identically.
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A unit of angle measure equal to of a complete revolution. There are 360 degrees in a circle. Degrees are indicated by the ° symbol, so 35° means 35 degrees.
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A line segment between two points on the circle or sphere which passes through the center. The word diameter is also also refers to the length of this line segment.
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A line segment where two faces of a polyhedron meet.
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A planar surface of a solid figure.
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The side of a right triangle opposite the right angle. Note: The hypotenuse is the longest side of a right triangle.
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The geometric figure formed by two points. A line is the straight path connecting two points and extending beyond the points in both directions.
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A pair of adjacent angles formed by intersecting lines. Angles 1 and 2 below are a linear pair. So are angles 2 and 4, angles 3 and 4, and angles 1 and 3. Linear pairs of angles are supplementary.
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All points between two given points (including the given points themselves).
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The point halfway between two given points.
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An angle that has measure more than 90° and less than 180°.
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The side facing a given angle in a triangle. It is the side not forming one arm of the angle.
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Two things that are located or facing directly across. Two opposite numbers are the two numbers that are equidistant from the origin on a number line but in opposite directions from the origin.
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Where two lines are both the same.
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The distance around the outside of a plane figure. For a polygon, the perimeter is the sum of the lengths of the sides.
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At a 90° angle. Note: Perpendicular lines have slopes that are negative reciprocals.
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| A flat surface extending in all directions. Any three noncollinear points lie on one and only one plane. So do any two distinct intersecting lines. A plane is a two-dimensional figure. |
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| The geometric figure formed at the intersection of two distinct lines. |
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| A closed plane figure for which all sides are line segments. The name of a polygon describes the number of sides. A polygon which has all sides mutually congruent and all angles mutually congruent is called a regular polygon. |
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| A solid with no curved surfaces or edges. All faces are polygons and all edges are line segments. |
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| prism A solid with parallel congruent bases which are both polygons. The bases must be oriented identically. The lateral faces of a prism are all parallelograms or rectangles. |
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| A proposition that has been or is to be proved on the basis of explicit assumptions. |
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| A polyhedron with a polygonal base and lateral faces that taper to an apex. A pyramid with a triangular base is called a tetrahedron. |
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| A line segment between the center and a point on the circle or sphere. The word radius also refers to the length of this segment. |
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| A line segment between the center and a point on the circle or sphere. The word radius also refers to the length of this segment. |
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| in three dimensional space that do not intersect and are not parallel. |
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| A three dimensional solid consisting of all points equidistant from a given point. This point is the center of the sphere. Note: All cross-sections of a sphere are circles. |
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| Two angles that add up to 180°. |
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| A proposition that has been or is to be proved on the basis of explicit assumptions. |
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| The "slope" of a vertical line. A vertical line has undefined slope because all points on the line have the same x-coordinate. As a result the formula used for slope has a denominator of 0, which makes the slope undefined.. |
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| A corner point of a geometric figure. For a polygon, vertices are where adjacent sides meet. For an angle, the vertex is where the two rays making up the angle meet. |
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are angles opposite one another at the intersection of two lines. Vertical angles are congruent.
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