standard_description: Prove theorems about parallelograms. Theorems include: opposite sides are congruent, opposite angles are congruent, the diagonals of a parallelogram bisect each other, and conversely, rectangles are parallelograms with congruent diagonals.
problem_activity: Problem 1
Below is triangle
$${\triangle ABC}$$
. Rotate this shape five times clockwise about the origin.
[IMG]
Problem 2
Which one doesn't belong? Give a reason why each of the quadrants does not belong with the rest.
[IMG]
Problem 3
Suppose
$${{{ABCD}}}$$
is a quadrilateral for which there is exactly one rotation, through an angle larger than 0 degrees and less than 360 degrees, which maps to itself.  Further, no reflections map
$${{{ABCD}}}$$
to itself.
What shape is
$${{{ABCD}}}$$
?


aligns: no