page+9.4


 * __9.4__**

Define angles formed by secants and tangents of circles.
 * Objectives:**


 * Develop and use theorems about measures of arcs intercepted by these angles.

Theorem 1**- If a tangent and a secant intersect on a circle at the point of tangencry, then the measure of the angle formed is 1/2 the measure of its intercepted arc.
 * __Theorems:__


 * Theorem 2**-The measure of an angle formed by two secants or chords that intersect in the interior of a circle is 1/2 the sum of the measures of the arcs intercepted by the angle and its vetical angle.


 * Theorem 3**- The measure of an angle formed by two secants that intersect in the eterior of a circle is 1/2 the distance of the measures of the intercepted arcs.


 * Theorem 4**- The measure of a secant-tangent angle with its vertex outside the circle is half the difference of the measure of the intercepted arcs.


 * Theorem 5**- The measure of a tangent-tangent angle with its vertex outside the circle is half the difference of the measures of the intercepted arcs, or the measre of the mahor arc minus 180 degrees.

link to 9.5