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11.1 Lines that intersect Circles
Definitions:
circle:
radius:
diameter:
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chord:
secant:
tangent:
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tangent circles:
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concentric circles
congruent circles
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common tangent:
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Theorems:
1. If a line is tangent to a circle, then it is perpendicular
to the radius drawn to the point of tangency.
(Converse also true)
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2. Tangent segments from the same external point are
congruent.
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Find the length of each radius. Identify the point of
tangency and write the equation of the tangent line at
this point.
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Examples:
1. Is CE tangent to circle D?
E
11
D
43
C
46
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2. BC is a tangent segment. Find x.
28
x
14
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3. AB and AD are tangent segments. Find x.
B
x-4
A
21
D