Exploring Isosceles Triangles (Version A)
In the GeoGebra Geometry app window below:
1) Use the CIRCLE WITH CENTER THROUGH POINT 
tool to construct a circle with center A that
passes through B.
2) Select the POINT ON OBJECT 
tool. With this tool selected, touch the circle in 2 different spots
to plot two different points, C and D, on the circle itself.
3) Use the POLYGON 
tool to construct the triangle ACD.
How would you classify this triangle by its sides? Why is this?
tool to construct a circle with center A that
passes through B.
2) Select the POINT ON OBJECT tool. With this tool selected, touch the circle in 2 different spots
to plot two different points, C and D, on the circle itself.
3) Use the POLYGON tool to construct the triangle ACD.
How would you classify this triangle by its sides? Why is this? Keep going: More directions appear below this applet.
4) Select the MOVE 
tool.
5) Use the ANGLE 
tool to find and display the measures of all 3 angles of this triangle.
tool.
5) Use the ANGLE tool to find and display the measures of all 3 angles of this triangle. 6)
What do you notice? (Be sure to select the MOVE tool again and move all 4 points around!)