AN ELEMENTARY GEOMETRY REVIEW

0.        The measure of an arc of a circle is equal to the measure on the central angle that intercepts the arc.

1.        The measure of an inscribed angle is equal to one-half the measure of it intercepted arc.

2.        An angle inscribed in a semicircle is a right angle.

3.        The measure of an angle formed by a tangent and chord is equal to on-half the measure of its intercepted arc.

4.        If the vertex of an angle falls within a circle, the measure of the angle is equal to one-half the sum of the measures of the two arcs intercepted by the sides of the angle and that of its vertical angle.

5.        If the vertex of an angle falls outside a circle and the sides of the angle intercept arcs on the circle, then the measure of the angle is equal to one-half the difference of the measures of the arcs intercepted by the sides of the angle.

6.        If inscribed angles of a circle intercept the same arc then they are congruent.

7.        If two chords intersect within a circle, the product of the measures of the segments of one will be equal to the product of the measures of the segments of the other.

8.        If a tangent segment and a secant segment are drawn to a circle from an external point, then the square of the measure of the tangent segment is equal to the product of the secant segment and its external portion.

9.        If two secant segments are drawn to a circle from an external point, then the product of the measures of one of these segments and its external  portion is equal to the product of the measures of the other with its external portion.