9.2+(WiBr56)

__Vocabulary__
 * secant**- line that intersects the circle at two points
 * tangent**- a line in the plane of the circle that intersects the circle at exactly one point
 * point of tangency**- plane of the circle that intersects the circle at exactly one point

__Secants and Tangents__ A secant to a circle is a line that intersects the circle at two points. A tangent is a line in the plane of the circle that intersects the circle at exactly one point, which is known as the point of tangency.

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

__Radius and Chord Theorem__ A radius that is perpendicular to a chord of a circle bisects the chord.

__Converse of the Tangent Theorem__ If a line is perpendicular to a radius of a circle at its endpoint on the circle, then the line is tangent to the circle.

__Theorem__ The perpendicular bisector of a chord passes through the center of the circle.

[[image:http://farm1.static.flickr.com/34/107392853_1fc9470bd6_m.jpg width="240" height="167" link="http://www.flickr.com/photos/photosbyjj/107392853/"]]
__Example__

Find the Radius a^2 + b^2 = c^2 (5)^2 + (24/2)^2 = c^2 25 +144 = c^2 square root 169 = square root c^2 13 = c radius = 13
 * In circle P, line AB is a tangent to point P at A, AC=24, DP= 5, AC = 31.2**

//**Find the distance of line PB**// a^2 x b^2 = c^2 (13)^2 + (31.2)^2= c^2 169 +973.44 = c^2 square root of 1142.44 = square root of c^2 33.8 = c segment PB = 33.8



For More Information http://regentsprep.org/regents/mathb/5A1/CircleAngles.htm http://library.thinkquest.org/20991/geo/circles.html#candr