Download - Section 9.1 Basic terms of Circles
Section 9.1Section 9.1Basic terms of Basic terms of Circles
What is a circle?What is a circle?CircleCircle: set of points equidistant from the : set of points equidistant from the
centercenterRadiusRadius: segment from the center to a point : segment from the center to a point
on a circleon a circle
ChordChord: segment with endpoints on a circle: segment with endpoints on a circle
SecantSecant: line that contains a chord: line that contains a chord
DiameterDiameter: a chord that contains the center : a chord that contains the center
of the circleof the circle
TANGENTTANGENTTangentTangent: a line that intersects the circle in : a line that intersects the circle in
exactly one pointexactly one point
Point of tangencyPoint of tangency: the point where the : the point where the tangent line intersects the circletangent line intersects the circle
Tangent Line
Point of Tang.
SpheresSpheresSphereSphere: set of all points in space at : set of all points in space at
the same distance from the centerthe same distance from the center
Congruent CirclesCongruent Circles
(or spheres) are circles (or spheres) that (or spheres) are circles (or spheres) that have congruent radiihave congruent radii
ConcentricConcentricConcentric circlesConcentric circles are circles that lie in the are circles that lie in the
same plane and have the same center. same plane and have the same center.
Concentric spheresConcentric spheres are spheres that have are spheres that have the same centerthe same center
Inscribed vs. CircumscribedInscribed vs. Circumscribed
InscribedInscribed in a circle means on the in a circle means on the insideinside of the circle.of the circle.Try to inscribe a triangle into a circle.Try to inscribe a triangle into a circle.
CircumscribedCircumscribed about a square means a about a square means a circle drawn around a square.circle drawn around a square.Try to circumscribe a rectangle about a Try to circumscribe a rectangle about a
circle.circle.
Inscribed vs. CircumscribedInscribed vs. Circumscribed
Which shape(s) are Which shape(s) are inscribed?inscribed?
Which shape(s) are Which shape(s) are circumscribed?circumscribed?
The square is inscribed in the circle.
The circle is inscribed in the triangle.
The triangle is circumscribed about the circle but NOT the square. (It must hit the endpoints on the square and it doesn’t.)
Copy the following Copy the following diagram.diagram.
1)1) Name three Name three radiiradii
2)2) Name a Name a diameterdiameter
3)3) Why is segment Why is segment TKTK not a chord? not a chord?
4)4) Name a tangent to circle Name a tangent to circle OO..
5)5) What name is given to point What name is given to point LL..
6)6) Consider segment Consider segment RSRS to line to line RSRS. . Which is a chord and which is a Which is a chord and which is a secant?secant?
, , OR OL OT
RLBoth endpoints aren’t ON the circleHL
Point of Tangency
Segment RS is a chord because it has endpoints.
S
O
E
HL
R
T
K
Practice ProblemsPractice Problems
Page 330 W.E. #1, 4, 5, 9 – 15, 18Page 330 W.E. #1, 4, 5, 9 – 15, 18