9.4+Angles+Formed+by+Secants+and+Tangents


 * 9.4.1 Theorem:** If a tangent and a secant intercet on a circle at the point of tangency, then the measure of the angle formed is 1/2 the measure of its intercepted arc.


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


 * 9.4.3 Theorem:** The measure of an angle formed by two secants that intersect in the exterior of a circle is 1/2 the difference of the measures of the intercepted arcs.


 * 9.4.4 Theorem:** The measure of a secant-tangent angle with its vertex outside the circle is 1/2 the difference of the measures of the intercepted arcs.


 * 9.4.5 Theorem:** the measure of a tangent-tangent angle with its vertex outside the circle is 1/2 the difference of the measures of the intercepted arcs, or the measure of the major arc minus 180 degrees.