Reflections

• You should have already constructed a triangle. Now me must draw a reflection line.

• Draw a line, highlight it, then under TRANSFORM, choose Mark Mirror.

Picture of Triangle and the Reflcetion Line DE

• Select your triangle. Under TRANSFORM, choose "REFLECT."

The Reflection of Triangle ABC across reflection line DE.

• Move your triangle around and note what happens. Move the line around and note what happens.

Moving the triangle past the reflection line.
Moving line

• Connect the Vertices of Triangle ABC to its corresponding vertices of Triangle A'B'C'. (It might be easier to make them different colors).

Connecting the Vertices

Notice the many shapes that are constructed after joining the segments. You should also notice the symmetry and the reflection line acts as the line of symmetry. If you were to measure the angles and edge length, you will find that they are congruent.

• Move the reflection line so that it goes through the triangle. Then move the vertices so that its reflection exactly coincides with the original figure.

Moving Line through the triangle
Moving the Vertices

• Now lets do the same thing with a quadrilateral. Draw a quadrilateral and create a reflection like you did with the triangle.

Quadrilateral and its reflection.

• Draw segments joining the corresponding vertices.

Connecting the vertices of both quadrilaterals.

Once again, the reflection line creates a line of symmetry.

• Move the line and vertices to see what happens.

Moving Line inside the quadrilateral

Write Up 3

Rotations

Translations