# IV. Angles Formed by Secants and Tangents

Drag the endpoints of the arcs to see how the measure of the angle DEB changes.

What is the relationship between the arc measures and the angle measures?
Move points A and D together such that segment AE is tangent to the circle.
Move points C and B together such that segment CB is tangent to the circle.
What is the relationship between the arc measures and the angle measures?

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