Matrix Reflections (Jump to: Lecture | Video )

Figure 1.

Above we have a triangle graphed on a coordinate plane. Its three points (x, y) are displayed in a vertex matrix.

Matrix multiplication can be used to reflect a figure. To reflect a figure is to flip it across its line of symmetry.

Figure 2.

Let's reflect triangle ABC across the x-axis.

Figure 3.

Now, we've reflected the triangle.