Circles Flashcards
Circle
A shape with all points a distance r from the center.
What is the center of a circle?
The point in the middle of a circle that is a distance r from all other points.
Radius
A line from the center to any point on the circle. Always remains the same length.
Diameter
A straight line passing through the center and connecting two points on the circle.
Congruent circles
Circles with the same radius.
Chord
A straight line going from one point on a circle to another.
Radius
A straight line from the center of a circle to any point on the circle.
Diameter
Two times the radius
Circumference
Distance around the circle, equal to pi times its diameter or pi times 2 times its radius.
Central angle
An angle formed by two radii.
Measure of an arc
An angle formed by two radii with endpoints at the arc’s endpoints.
Length of an arc
The distance along an arc from one endpoint to another.
Area of a circle
The area enclosed by a circle.
Sector
A region of a circle between two radii.
Area of a sector
The area enclosed within a sector of a circle.
Tangent
A line that intersects a circle at only one point.
Point of tangency
The point on a circle that a tangent intersects.
Inscribed
A shape, typically a polygon, whose vertices lie on the circumference of a circle. If it’s a circle inscribes in another shape, the circumference of the circle touches each side of the outer shape.
Circumscribed
The outer shape that encloses an inscribed shape.
Concentric circles
Circles with the same center.
Equation for the area of a circle
A=pi*r^2
Equation for the circumference of a circle
A=2pir or pi*d
