Geometry Glossary - C
 

Central angle:

an angle whose vertex is the center of a circle

Chord of a circle:

a line segment whose endpoints are on the circle

Circle:

the set of all point equidistant from a given point, called the radius

Circumcenter:

The center of a circle that is circumscribed around another figure. The circumcenter of a triangle is the center of the circle circumscribed about it. In the illustration shown below, Point P is the circumcenter of the triangle.

Circumference:

the distance around a circle (or a great circle of a sphere). The formula for circumference is d or 2r, where d stands for diameter, and r stands for radius

Circumscribed polygon:

a polygon that has all of its sides tangent to a circle

Coincident Lines:

two lines having more than two points in common; i.e., they lie on top of one another; in the plane, coincident lines have the same slope and y-intercept

Collinear:

Points that lie on the same line

Compass:

an instrument used for drawing circles and measuring distances. A compass consists of two legs hinged together at one end

Complementary angles:

two angles that have measures that total 90 degrees; one angle can be called the "complement" of the other

Concave polygon:

a polygon is concave if at least one of its diagonals is exterior

Diagonals in red.

Concurrent Lines:

two or more lines that have a point in common

Congruent:

adjective describing figures that have equal corresponding measures

 

Congruent triangles:

triangles that have congruent corresponding parts; in other words, corresponding angles have equal measures and corresponding sides have equal lengths

Abbreviated: CPCTC = Corresponding Parts of Congruent Triangles are Congruent

ABC  EDF
	A E
	B D
	C F

Conic:

an adjective describing any surface which has one base connected to a point, not in the plane of the base, by a smooth surface or triangular lateral faces; both cones and pyramids are conical

Conic Section:

the intersection of a plane and double cone (two congruent right cones aligned tip to tip with bases parallel); the conic sections are ellipse, circle, hyperbola, and parabola

Conjecture:

a statement proposing that some observed characteristic might be true in all cases; further testing and observation may validate or disprove the conjecture (also called supposition or hypothesis)

Conjunction:

 two statements joined by the word "and;" the conjunction is true if both statements are true

Construct:

to draw a geometrical figure so as to fulfill given conditions

Convex Polygon:

a polygon is convex if all of its diagonals are interior

Coordinate Plane:

the grid formed by vertical and horizontal number lines that intersect at zero; also called the Cartesian Plane (named for Rene Descartes, its founder)

Coordinates:

the number assigned to the graph of a point on a number line;

OR the ordered pair (x, y), which describes the location of a point in the xy-plane;
OR the ordered triple (x, y, z), which describes the location of a point in space

Coplanar:

points or lines that lie in the same plane

Corresponding angles:

these pairs occur when two lines are intersected by a transversal; they occupy the same position with respect to the transversal and the original lines

Cosecant:

1. in a right triangle, the ratio of the measure of the hypotenuse to the measure of the opposite side
2. a trigonometric ratio equal to the reciprocal of the sine of the angle

Cosine:

1. in a right triangle, the ratio of the measure of the adjacent side to the measure of the hypotenuse
2. a trigonometric function equal to the x-coordinate of the point of intersection of the terminal ray of an angle in standard position with the unit circle

Cotangent:

1. in a right triangle, the ratio of the measure of the adjacent side to the measure of the opposite side
2. a trigonometric ratio equal to the reciprocal of the tangent of the angle

Coterminal angles:

angles are coterminal if they share the same terminal ray and are in standard position

Corresponding angles:

angles that are formed on the same side of a transversal

Cylinder:

the surface of a cylindric solid whose parallel bases are congruent circles

Cylindric:

an adjective describing any surface that has two congruent, parallel bases; both prisms and cylinders are cylindric surfaces