standard_description: Prove the slope criteria for parallel and perpendicular lines and use them to solve geometric problems (e.g., find the equation of a line parallel or perpendicular to a given line that passes through a given point).
problem_activity: Task
Rhianna has learned the SSS  and SAS congruence tests for triangles and she wonders if these tests might work for parallelograms.
Suppose $ABCD$ and $EFGH$ are two parallelograms all of whose corresponding sides are congruent, that is $|AB| = |EF|, |BC| = |FG|, |CD| = |GH|,$ and $|DA| = |HE|$.  Is it always true that $ABCD$ is congruent to $EFGH$?
Suppose $ABCD$ and $EFGH$ are two parallelograms with a pair of congruent corresponding sides, $|AB| = |EF|$ and $|BC| = |FG|$.  Suppose also that the included angles are congruent,
$m(\angle ABC) = m(\angle EFG)$.  Are $ABCD$ and $EFGH$ congruent?


aligns: no