# geometry

## 20 terms

### circle

the set of points in a plane at a given distance from a given point in that plane

the length of a line segment between the center and circumference of a circle or sphere

### cord

a segment whoes endpoints lie on a cicle is a chord

### diameter

the length of a straight line passing through the center of a circle and connecting two points on the circumference

### secant

ratio of the hypotenuse to the adjacent side of a right-angled triangle

### tangent

ratio of the opposite to the adjacent side of a right-angled triangle

### sphere

the set of all points in space at a given distance from a given point is a sphere

### congruent circles

circles that are congruent if they have congruent radii

### congruent spheres

spheres that are congruent if they have congruent radii

### concentric circles

circles that lie in the same plane and have the same center are concentric

### concentric spheres

concentric spheres have the same center

### inscribed polygon

a polygon is inscrived in a circle if each vertex of the polygon lies on the circle

### circumscribed circle

a circle is circumscrived about a polygon if each vertex of the polygon lies ont he circle

### common tangent

a line that is tangent to each of two coplanar circles is a common tangent

### tangent circles

two cirlces that are tangent to the same line at the same point

### circumscribed polygon

a polygon is circumscribed about a circle if each of its sides is tangent to the circle

### inscribed circle

a circle is inscribed in a polygon if each of the sides of the polygon is tangent to the circle

### central angle

an angle with its vertex at the centrer of a circle is a central angle

### arc

any unbroken part of the circumference of a circle or other curved line.

### measure of an arc

the measure of a minor arc is the measure of its central angle