[size=150]1) Use the POLYGON [icon]/images/ggb/toolbar/mode_polygon.png[/icon] tool to construct triangle [i]ABC[/i]. [br]2) Select the ANGLE [icon]/images/ggb/toolbar/mode_angle.png[/icon] tool. Then click anywhere inside the polygon. [br]3) Go to the Algebra view (click calculator icon upper left). [br][br]4) Calculate the sum of the measures of the interior angles of this triangle. [i]Be sure to add the [br] Greek letters when doing so! [/i](See the video right below this app to see how to quickly do [br] this in GeoGebra). [br][/size]
[size=150]Select the MOVE [icon]/images/ggb/toolbar/mode_move.png[/icon] tool in the app above. Move any one (or more) of the triangle's vertices around. What can we conclude about the [b]sum of the measures of the interior angles[/b] of any triangle? [/size]
[size=150]Select the MOVE [icon]/images/ggb/toolbar/mode_move.png[/icon] tool. Move any one (or more) of the triangle's vertices around. [br]What can we conclude about the [b]exterior angles[/b] of this triangle? [i]Be specific in your response. [/i][/size]