Angle formed by a Secant & Tangent: What Do You See? (V1)

Mess around with the applet below for a few minutes.[br]Feel free to move the [b]BIG POINTS[/b] around before you start dragging the slider.[br][br]Be sure to drag the slider slowly and pay careful attention to what happens. [br][br]After you drag the slider to the end, press "Reset Slider".[br]Change the location of the [color=#c51414]BIG RED POINT[/color] and the [color=#b20ea8]BIG PURPLE POINT[/color].[br]Then move the slider slowly again. [br][br]Have fun with this applet, and then answer the questions that appear below the applet.
Angle formed by a Secant & Tangent: What Do You See? (V1)
The purple angle (you see when you drag the slider to the end) is called an [b]angle formed by a secant and a tangent[/b]. [br]Given what you've just observed, answer the following questions: [br][br]Suppose the [color=#c51414]red arc measures 150 degrees[/color] and the [color=#0a971e]green arc measures 80 degrees[/color]. [br]If this were so, what would the measure of the purple angle be? [br][br]Suppose the [color=#c51414]red arc measures 120 degrees[/color] and the [color=#0a971e]green arc measures 30 degrees[/color].[br]If this were so, what would the measure of the purple angle be? [br][br]If the measure of the purple angle was 30 degrees and the [color=#c51414]measure of the red arc was 190 degrees[/color], what would the [color=#0a971e]measure of the green arc be[/color]? [br][br]Now, drag the red point to the right. Go as far as you can. What happens? [br]Why did the "secant" ray disappear? [br][br]From your observations, [b]describe how to find the measure of an angle formed by a secant and a tangent[/b]. Be sure to use the phrase [b]"intercepted arc(s)"[/b] at least once in your description. Please be as specific as you can.

Information: Angle formed by a Secant & Tangent: What Do You See? (V1)