# Double Reflection over Intersecting Lines

Move the slider to change the angle of the intersecting lines.

You can change the angle of intersecting lines by moving the Black Slider.

- Click the Reflection in Line 1 box. Click and drag around Point D. How does the location of Point D affect the position of the image triangle A'B'C'?
- Click the Reflection in Line 2 box. Take turns dragging Point D and moving the Black Slider. How does moving Point D change the position of A"B"C"? Why do you think this is? How does changing the angle of the intersecting lines change the position of A"B"C"? Why do you think this is?
- Click Show m<AEA". Move the Black Slider to get a sense of what this angle measure shows. Click Show Rotation. Move the Red Rotation Slider until you map the Red rotating triangle with triangle A"B"C". (You can use the left and right arrow buttons on your keyboard if you have trouble getting it exactly matched). What is the relationship between the angle of rotation and the angle between the intersecting lines?

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