Angles in Same Segments (Proof)

Below shows a circle, with centre O.
The points A, B, C, D and X are points on the circumference of the circle.

You can:

• shift the point O to change the position of the circle
• shift the point X to change the size of the circle
• shift the points A and B to change the position and size of the segment ACDB
• shift the points C and D to change their positions

Instructions:

1. Adjust the position and size of the segment ACDB.
2. Adjust the position of the points C and D.
3. Check all boxes.
4. Repeat steps 1 ~ 3 for other positions and sizes of the segment ACDB and the points C and D.

Note: To see the animation, check all boxes, then click on the "play" button (at bottom left).



Download the GeoGebra file: http://www.geogebratube.org/material/download/format/file/id/41524