Geometry Honors Section 9.2

Tangents to Circles

A line in the plane of a circle may or may not intersect the circle.

There are 3 possibilities.

A *secant to a circle is a line which intersects the circle in two points.

A line in the plane of a circle may or may not intersect the circle. There are 3 possibilities.

A

B

chord a is AB

secant a is AB

A *tangent to a circle is a line, in the plane of the circle, that intersects the circle in exactly one point.

This point of intersection is known as the _______________point of tangency.

Tangent TheoremIf a line is tangent to a circle, then

it is perpendicular to the radius drawn to the point of tangency.

64 68

106 222

b

b

A segment is tangent to a circle if the segment is part of a tangent line and one endpoint is the point of tangency.

segment

tangenta is AB

Tangent Segments Theorem

If two segments are tangent to a circle from the same exterior point,

then the tangent segments are congruent.

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081

018