###
central angle

an angle whose vertex is the center of the circle.

###
minor arc

part of a circle that measures less than 180 degrees

###
major arc

part of a circle that measures between 180 degrees and 360 degrees

###
semicircle

an arc whose endpoints are half the circle; endpoints are the diameter of the circle.

###
congruent arcs

2 arcs of the same circle or of congruent circles that have the same measure.

###
inscribed angle

and whose vertex is on a circle and whose sides contain chords of the circle

###
interepted arc

the arc that lies in the interior of an inscribed angle and has endpoints on the angle.

###
inscribed polygon

polygon whose vertices all lie on a circle.

###
circumscribed circle

circle with an inscribed polygon

###
circle

set of all points in a plane that are equidistant from a given point

###
radius

distance from the center of a circle to a point on the circle

###
congruent circles

2 circles that have the same radius

###
diameter

chord that passes through the center of a circle

###
chord

segment whose endpoints are points on the circle

###
secant

segment that intersects a circle twice.

###
tangent circles

circles that intersect in one point

###
concentric

circles that have a common center

###
common tangent

a line or segment that is tangent to 2 circles

###
interior of a circle

all points of the plane that are inside a circle

###
exterior of a circle

all points of the same plane that are outside a circle

###
point of tangency

point where tangent line meets circle line

### Please allow access to your computer’s microphone to use Voice Recording.

## We can’t access your microphone!

### Click the icon above to update your browser permissions and try again

Example:

### Reload the page to try again!

Reload

## Press Cmd-0 to reset your zoom

## Press Ctrl-0 to reset your zoom

### It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

## Your microphone is muted

### For help fixing this issue, see this FAQ.