A flower bed in a school is in the shape of a parallelogram and its perimeter is 42 meters. One side is 13 meters long and the other three sides are 13 meters, 8 meters and 8 meters long.

Analysis: parallelogram, opposite sides are equal, one side is 13 meters, there must be an opposite side that is also 13 meters, then the sum of the remaining two sides is 16 meters, so the remaining set of opposite sides is 8 meters long, so the other three sides are 13 meters, 8 meters, and 8 meters long.

Based on the fact that since the opposite sides of a parallelogram are each equal, its perimeter is the sum of the adjacent sides times 2.

Formulation:

(42-13*2)÷2

=(42-26) ÷2

=16 ÷2

=8

Answer: the lengths of the other three sides are 8 meters , 13 meters and 8 meters.

Extension:

1. Two sets of opposite sides of a parallelogram are each equal.

2. Two sets of opposite angles of a parallelogram are each equal.

3. The neighboring angles of a parallelogram are complementary.

4. The heights of parallels sandwiched between two parallel lines are equal.

5. The diagonals of a parallelogram are equal to each other.

6. The figure obtained by connecting the midpoints of the sides of any quadrilateral is a parallelogram.

7. The area of a parallelogram is equal to the product of the base and the height.

8. A line through the intersection of the diagonals of a parallelogram divides the parallelogram into two equal parts.

9. A parallelogram is not axisymmetric, it is centrosymmetric, and the center of symmetry is the intersection of the two diagonals.

10, the diagonal of a parallelogram divides the area of the parallelogram into four equal parts.