12-1 Tangent Lines

Definitions

• A tangent to a circle is a line in the plane of the circle that intersects the circle in exactly one point called the point of tangency.

Theorem 12-1

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

Theorem 12-2

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

Theorem 12-3

• Two segments tangent to a circle from a point outside the circle are congruent.

Example #1

• Find x.

117˚x˚

360-117-90-90=63˚

Example #2

• Find the distance between the centers of the pulleys.

26.5 in.

9.3

in.

4.3

in.

52 + 26.52 = c2

27.0 in

Today's Assignment

• WS 12-1