Section 9 1 notes (slide share)
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Circle – the set of all points in a plane a given distance away from a center
point.
A
Circle – the set of all points in a plane a given distance away from a center
point.
A
A circle is named by its center point. For example: Circle
A or A.
Circle – the set of all points in a plane a given distance away from a center
point.
A
A circle is named by its center point. For example: Circle
A or A.
Radius – the “given distance away from the center point” of a circle; a segment that joins the center to a
point on the circle.
Circle – the set of all points in a plane a given distance away from a center
point.
A
A circle is named by its center point. For example: Circle
A or A.
Radius – the “given distance away from the center point” of a circle; a segment that joins the center to a
point on the circle.
Radius (r) Plural: Radii
Sphere – the set of all points a given distance away from a center
point.
Chord – a segment whose endpoints lie on on the circle.
Chord – a segment whose endpoints lie on on the circle.
Example: DC
C
D
Chord – a segment whose endpoints lie on on the circle.
Example: DC
A BC
D
Diameter – a chord that passes through the center of the circle. Example: AB
A diameter is twice the length of a radius.
Secant – a line that contains a chord.
Example: ABA
B
Secant – a line that contains a chord.
Example: ABA
B
**Note: A chord and a secant can be named using the same letters. The
notation tells you whether it is a secant or a chord. A secant is a line; a chord is a
segment.**
Secant: AB Chord: AB
Tangent – a line that intersects a circle at exactly one point.
A
B
Example: AB
Tangent – a line that intersects a circle at exactly one point.
Not a tangent
!
A
B
Example: AB
Tangent – a line that intersects a circle at exactly one point.
Not a tangent
!
A
B
The point at which the circle and the tangent intersect is called the
point of tangency.
Example: AExample: AB
Congruent Circles – circles with
congruent radii.5cm
5cm
Congruent Circles – circles with
congruent radii.5cm
5cm
Concentric Circles – circles with the same center point.
A polygon is inscribed in a circle and the circle is circumscribed about the polygon when all of the vertices of the polygon lie on the circle.
A polygon is inscribed in a circle and the circle is circumscribed about the polygon when all of the vertices of the polygon lie on the circle.
A polygon is inscribed in a circle and the circle is circumscribed about the polygon when all of the vertices of the polygon lie on the circle.
This pentagon is inscribed inside of the
circle.
When each side of a polygon is tangent to a circle, the circle is said to be inscribed in the polygon.
When each side of a polygon is tangent to a circle, the circle is said to be inscribed in the polygon.
When each side of a polygon is tangent to a circle, the circle is said to be inscribed in the polygon.
This circle is inscribed
inside of the pentagon.