CHAPTER+9.4+T.0

ANGLES FORMED BY SECANTS AND TANGENTS
__OBJECTIVES:__ 1.Define angles formed by secants and tangents of circles. 2.Develope and use theorems about measures of arcs intercepted by these angles


 * __DEFINITIONS AND BLUE BOXES:__

THEOREM 1-** If a tangent and a secant (or a chord) intersect on a circle at the point of tangency, then the measure of the angle formed is _ the measure of its intercepted arc.
 * THEOREM 2-** The measure of an angle formed by two secants that intersect in the exterior of a circle is _ the _ of the measures of the intercepted arcs.
 * THEOREM 3-** The measure of an angle formed by two secant or chords that intersect in the interior of a circle is _ the _of measures of the arcs intercepted by the angle and its vertical angle.
 * THEOREM 4-** The measure of a secant - tangent angle with its vertex outside the circle is ?
 * THEOREM 5-** The measuer of a tangent - tangent angle with its vertex outside the circle is _.


 * __EXAMPLE:

__** with using the 1st theorem from chapter 9.3 u can easly do this problem find the angle avc angle avc = 1/2m arc av which = 1/2 (100) this = 50