geometry: chapter 9 Flashcards
circle
a set of points in a plane equidistant from a given point in the plane
center
the given point
radius
any segment that joins the center to a point of the circle
chord
segment whose endpoints lie in the circle
secant
a line that contains a chord
diameter
chord that contains the center of the circle
tangent
line in the plane of a circle that intersects the circle at exactly 1 point
point of tangency
point that the tangent intersects the circle
sphere
set of all points in space at a given distance from a given point
congruent circles
have congruent radii
concentric circles
circles that line in same plane and have the same center
concentric spheres
spheres that have same center
inscribed/ circumscribed polygon
vertices of the polygon lie on the circle
Theorem 9-1
If a line is tangent to a circle then the line is perpendicular to the radius drawn to the point of tangency.
Corollary to Theorem 9-1
Tangents to a circle from a point are congruent
Theorem 9-2
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
a line that is tangent to each of two coplanar circles
common internal tangent
intersects the segment joining the centers of the circles
common external tangent
does not intersect the segment joining the centers
tangent circles
coplanar circles that are tangent to the same line at the same point
central angle
angle with its vertex at the center of the circle
minor arc
part of circle that is smaller than half
major arc
part of circle that is greater than half
semicircle
arc with the endpoints at the diameter