# IM2 5.1 How Do You Know That?

## Experiment #1

What does this experiment reveal about the sum of the interior angles of the triangles you tested, and how does it do so?

For this experiment, you are given a triangle. Use the slide tool to rotate the triangle 180 degrees around the midpoint of the side, then use the other slide tool to rotate the new "image" triangle 180 degrees about the midpoint of the other side.

## Experiment #2

What does this experiment reveal about the sum of the interior angles of the triangles you cut out, and how does it do so?

Do you think you can rotate all triangles in the same way about the midpoints of its sides and get the same results? Why or why not?

Will the second figure in the sequence always be a parallelogram? Why or why not?

Will the last figure in the sequence always be a trapezoid? Why or why not?