The document defines key terms related to circles and tangents, including: a circle as points equidistant from a center point; a radius and diameter; a chord as a segment with endpoints on the circle; a secant as a line intersecting a circle at two points; and a tangent as a line intersecting a circle at exactly one point. It states that a tangent line is perpendicular to the radius drawn to the point of tangency, and that for two segments from the same exterior point to both be tangent to a circle, they must be congruent.

1. Terms of Endearment
Tangents to Circles: 10.1

2. Circle
• The set of all points in a plane that
are equidistant from a given point
(called the center)
• Radius – segment with endpoints at
the center and on the circle
• Diameter – segment with endpoints
on the circle and passes through the
center (a chord)

3. Chord
• Segment with endpoints on the
circle…no particular location in the
circle
• Here are several to look at:

4. Secant
• Line that intersects the circle in two
points
• Think of it as a chord, but instead of
being a segment, think line…
because it is a line.

5. Tangent
• Line in the same plane as the circle
that intersects the circle in exactly
one point

6. Theorem
• If a line is tangent to a circle, it is
perpendicular to the radius drawn to
the point of tangency.

7. Converse
• In order for the lines to be tangent,
the radius must be perpendicular to
the lines

8. Another Theorem
• If two segments are from the same
exterior point and both are tangent
to the circle, they are congruent to
each other.