Circles Flashcards
Centre
Given point
Circle
Set of points in a plane at a given distance from a given point in that plane
Radius
Given distance
Chord
Segment whose end points lie on a circle
Secant
Line which contains a chord
Diameter
Chord that contains the centre of a circle
Tangent
Line in plane of the circle that intersects circle in exactly one point
Point of tangency
Point where tangent intersects circle
Congruent circles
Circles with congruent radii
Concentric circles
Circles that lie in same plane and have same centre
When is a polygon inscribed or a circle circumscribed? (Or vice versa)
When each vertex of the polygon lies on the circle
If a line is tangent to a circle…
Then the line is perpendicular to the radius drawn to the point of tangency
Tangents to a circle from a point are…
Congruent
If a line in the plane of a circle is perpendicular to a radius at its outer endpoint…
Then the line is tangent to the circle
Common tangent
Line that is tangent to each of the two coplanar circles
Common internal tangent
Intersects the segment joining the centres