[color=#0000ff][b]Theorem: [/b][/color][br][br]If two lines cross to form [color=#9900ff][b]congruent, adjacent angles[/b][/color], then those [b]lines are perpendicular.[/b] [br][br][br]Write a 2-column (or paragraph) proof that formally proves what this applet informally illustrates. [br][i][color=#cc0000]Be sure to set up an appropriate diagram, state what is given, and state what needs to be proven. [br]Then prove it! [/color][/i] [br][br]