G.GCO.11 Alternate Angle Bisector Construction

Creation of this applet was inspired by a [url=https://twitter.com/solvemymaths/status/776842316938113024]tweet[/url] by [url=https://twitter.com/solvemymaths]@solvemymaths[/url]. [br][br][color=#1e84cc][b]Here's another simple means to construct the bisector of an angle using a compass & straightedge. [br][/b][/color][br][br]Why does this method work? [br]Write a formal (2-column or paragraph) proof that justifies why this method of construction is valid.
Quick (Silent) Demo: 1:00 to END

Information: G.GCO.11 Alternate Angle Bisector Construction