geometry 11-1 circle basics divide your paper into eight boxes. draw a circle in each box, but leave...
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Geometry 11-1 Circle Basics
Divide your paper into eight boxes. Draw a circle in each box, but leave some room to write a definition.
Center of a circle
The point in the middle of the circle. Equidistant from every point on the circle.
C
Radius
A line segment from the center of a circle to the edge of the circle.
r
Chord
A line segment that connects two points on the edge of the circle.
B
Diameter
A chord that goes through the center of the circle.
d
A
Secant
A line that intersects a circle at two points.
B
Tangent
A line that intersects a circle at exactly one point.
A
A
B
Point of Tangency
The point where a tangent intersects a circle.
P
chords:
secant:
tangent:
diameter:
radii:
QR and ST
ST
PQ, PT, and PS
UV
ST
Draw this is box 8
Theorem 1
• If two segments are tangent to a circle from the same external point, then the segments are congruent.
Example
x + 25
3x – 5
AQ and AP are tangent to circle L. Determine the length of each tangent line.
P
Q
A
L
Theorem 2
• If a line is tangent to a circle, then it is perpendicular to the intersecting radius.
A
m
m is perpendicular to AB
B
Example
5 cm
B
C
Line segment AB is tangent to circle C. Determine the length of BC if the length of AB is 12 cm.
A