AC and BD are parallel secants. A. Check the box to highlight arcs and show arc measures. Drag the points to adjust the lines. 1. How do the arcs change? When are they largest? Smallest? 2. How do the arc measure relate to each other? B. Check the box so that the arcs and arc measures are not shown. Click to show the transversal and alternate interior angles. Drag the points to adjust the lines. 1. What kind of angle pairs are angles CAD and BDA? 2. Which arcs do CAD and BDA intercept? 3. How do the measures of angles CAD and BDA relate? 4. Can you explain why arcs AB and DC will always be congruent by describing the relationship between CAD and BDA?