What geometric property of parabolas is dynamically illustrated here? [br](Note: The 2nd [color=#0000ff]blue ray[/color] is parallel to the parabola's axis of symmetry.) [br]Also, feel free to drag any of the [b]black points[/b]anywhere!
[b][color=#000000]Theorem:[/color] [/b][br]If a line is drawn tangent to a parabola, it makes [color=#ff00ff][b]equal angles[/b][/color] with the [color=#0000ff][b]line through this point that's parallel[/b][/color] to the parabola's [color=#980000][b]axis of symmetry[/b][/color] AND with the [color=#0000ff][b]line[/b][/color] containing this point and the focus.