Create an ellipse with the intersection point of two tangents and animate the construction by following the construction steps below.

Note: If you're using the Mobile App make sure that the chosen Labeling option is New Points Only. You can change this by going to the Settings in the app's menu and then selecting General.

1.		Create an ellipse using the Ellipse tool.
2.		With the Line tool select point A and create a point D on the outline of the ellipse.
3.		Create point E by selecting the second intersection point of the created line and the outline of the ellipse.
4.		Select the Tangents tool to create the tangents of the ellipse at point D and E. For the first tangent select the point D and then the outline of the ellipse. Repeat this for the second tangent with point E.
5.		Create the intersection point F of the two tangents using the Intersect tool.
6.		Change the color of point F to red.
7.		Move point D. Note: When using the Online or Desktop App you can animate point D by selecting it and then choosing Animation.

Note: Open the context menu of point F by selecting the More button and activate Show Trace. Then move point D again to be able to observe the trace of point F.