D5. The slider reflection
Looking for footprints
GeoGebra does not have a tool for slider reflection, but it is very simple to make this transformation with an instruction that combines two transformations. The slider reflection combines reflection and a translation with the same direction.
1st. Activate the "Vector" tool 
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2nd. Click on two points in the Graphics View to create the point "A" the point "B" and the vector "u".
3rd. Activate the "Line" tool 
and click on the points "A" and "B" to create the line "f". As the straight line and the vector are defined with the same points, they have the same direction.
4th. Activate the "Move" tool 
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5th. Type into the Input Bar the command foot2 = Translate(Reflect(foot1, f), u) and press the "Enter" key to execute it. Realize that there is a command inside another command.
6th. Type into the Input Bar the command foot3 = Translate(Reflect(foot2, f), u) and press the "Enter" key to execute it.
7e. Type into the Input Bar the command foot4 = Translate(Reflect(foot3, f), u) and press the "Enter" key to execute it.
Activate the "Move" tool and move the points, the original line and foot.
The two curved arrows located in the upper right corner of the Graphics View allow you to reset the activity.
If the activity is correct, you will get 10 points automatically.
.
2nd. Click on two points in the Graphics View to create the point "A" the point "B" and the vector "u".
3rd. Activate the "Line" tool and click on the points "A" and "B" to create the line "f". As the straight line and the vector are defined with the same points, they have the same direction.
4th. Activate the "Move" tool .
5th. Type into the Input Bar the command foot2 = Translate(Reflect(foot1, f), u) and press the "Enter" key to execute it. Realize that there is a command inside another command.
6th. Type into the Input Bar the command foot3 = Translate(Reflect(foot2, f), u) and press the "Enter" key to execute it.
7e. Type into the Input Bar the command foot4 = Translate(Reflect(foot3, f), u) and press the "Enter" key to execute it.
Activate the "Move" tool and move the points, the original line and foot.
The two curved arrows located in the upper right corner of the Graphics View allow you to reset the activity.
If the activity is correct, you will get 10 points automatically.