Geometry Lesson 4.2 Reflections
Explore Reflections with GeoGebra
Watch the video to learn how to create a reflection in GeoGebra. After completing your reflection, answer the questions.
THE STEPS IN VIDEO:
DETAILED STEPS:
1. Construct a triangle ABC with the "Polygon" tool. 
2. Construct an axis of symmetry with the "Line" tool.
3. Construct the reflection of your pre-image with the "Axial symmetry" tool and change the color of the image.
4. Connect the vertices A and A', B and B' then C and C' with the "Line" tool and transform your lines into dotted lines.
5. Place a point F at the intersection of the line AA' and the axis of symmetry, a point G at the intersection of the line BB' and the axis of symmetry and a point H at the intersection of the line CC' and the axis of symmetry with the "Intersection" tool.
6. Display the measures of the 3 angles at the 3 intersections on the axis of symmetry with the "Angle" tool.
7. Display the measurements of segments AF, FA', CG, GC', BH and HB' with the "Distance or Length" tool.
8. Display the measurements of the 3 sides of the image and those of the pre-image with the "Distance or Length" tool.
9. Move your axis of symmetry with the "Move" tool. Observe what happens.
10. Modify your initial figure with the "Move" tool. Observe what happens.
2. Construct an axis of symmetry with the "Line" tool.
3. Construct the reflection of your pre-image with the "Axial symmetry" tool and change the color of the image.
4. Connect the vertices A and A', B and B' then C and C' with the "Line" tool and transform your lines into dotted lines.
5. Place a point F at the intersection of the line AA' and the axis of symmetry, a point G at the intersection of the line BB' and the axis of symmetry and a point H at the intersection of the line CC' and the axis of symmetry with the "Intersection" tool.
6. Display the measures of the 3 angles at the 3 intersections on the axis of symmetry with the "Angle" tool.
7. Display the measurements of segments AF, FA', CG, GC', BH and HB' with the "Distance or Length" tool.
8. Display the measurements of the 3 sides of the image and those of the pre-image with the "Distance or Length" tool.
9. Move your axis of symmetry with the "Move" tool. Observe what happens.
10. Modify your initial figure with the "Move" tool. Observe what happens.BUILD YOUR THINKING HERE:
QUESTION 1
Change the shape of your pre-image. What do you notice about the corresponding side lengths of the pre-image and image?
QUESTION 2
Change the shape of your pre-image. What do you notice about the corresponding angle measures of the pre-image and image?
QUESTION 3
What is the relationship between the three dashed lines?
QUESTION 4
What do you notice about the angles formed from the dashed lines and the line of reflection?
QUESTION 5
The line of reflection is the ___________ of the dashed segments connecting the corresponding pre-image and image points.