[color=#000000][b]Introduction[br][/b]What makes a triangle a triangle?  [br]What makes a triangle a unique triangle – one of a kind?  [br]It’s all about sides and angles.  [br][br]In this activity you will explore the sides of a triangle, noticing when a set of sides, line segments, can determine a unique triangle, more than one triangle, or no triangle at all.[br][br]In the [i]GeoGebra [/i]workspace, there are three sets of sides that can be used to attempt to construct triangles in the open workspace: Set A, Set B, and Set B.[br][br]The red line segments are of fixed length.  [br]The black line segment has an adjustable length, changed by dragging the black endpoint.  [br]They can be moved about the workspace using the blue endpoint.  [br]They can be swiveled using the orange endpoint.[br][br][b]Step 1[br][/b]Use the MOVE tool to drag and manipulate line segments in Set A onto the open workspace.  Try to make a triangle with the given segments as sides. Connect the end-points are carefully as you can. Can you construct a triangle with these three line segments?  Explain your answer.[br][br][b]Step 2[br][/b]Move the line segments from Set A back into their box. Use the MOVE tool to drag and manipulate line segments in Set B onto the open workspace.  Try to make a triangle with the given segments as sides. Connect the end-points are carefully as you can. Can you make a triangle with these three line segments?  Can you make more than one? [br][br][b]Step 3[/b][br]Move the line segments from Set B back into their box. Use the MOVE tool to drag and manipulate line segments in Set C onto the open workspace.  [br][br]Try to make a triangle with the given segments as sides.[br]Can you make a triangle with these three line segments?  [br]Can you make more than one? How many?[br][br][b]Conclusion[/b][br]Summarize what you have learned about the sides of triangles and whether or not, given a set of sides, you can create triangle, more than one triangle, or no triangle at all.[/color]