The Relationship Between Circles and Right Triangles . Consider a circle of radius r with a central angle α, such as shown below. Let's draw a line segment from point P down to (and perpendicular with) the horizontal radius. This construction forms a right triangle with a hypotenuse of length r (the radius of the circle). If two secants (chords) intersect in the interior of a circle, then the measure of each angle is one half the sum of the measures of the arcs intercepted by the angle and its vertical angle. m<APB = ½ (mABD+ mCD) Open the book to page 831 and read example 2. Example: Find m<AEB. circumference of a circle 5. explore the relationship between the radius and the length measure of the circle (circumference) finding an of pi unknown6. correctly apply the formula for circumference of a circle E. Use facts about supplementary, complementary, vertical, and adjacent angles to write and solve equations for an angle in a figure relationships among the angles of an inscribed quadrilateral. Open a new page in Cabri II and follow the instructions below. Laboratory One 1. Draw a circle and label the center O. [Circle Tool] 2. Draw a segment whose endpoints lie on the circle and label the points A and B. [Segment Tool] 3. Place a point anywhere on the circle and label it C. Jul 08, 2019 · If you found these worksheets useful, please check out Tangents to Circles Worksheet PDF, Circumscribed and Inscribed Circles Worksheets, Law of Sines and Cosines Worksh eet PDF, Double angle and Half-Angle identities with Answers, Double Angle and Half Angle Formulas Worksheet, Graphing Inverse Functions Worksheet wi th Answers PDF, Inverse ...