7) The missing variables of the parallelogram are:
c = 6
d = 10
How to find the diagonals of the parallelogram?
We know that the seven properties of a parallelogram are:
1) opposite sides with the same length.
2) opposite sides parallel to each other.
3) opposite angles with the same measure.
4) Consecutive angles are supplementary.
5) Diagonals bisect each other.
6) Each diagonal divides the parallelogram into two congruent triangles.
7) The sum of the squares of the sides is equal to the sum of the squares of the diagonals
Since the diagonals bisect each other, then we can say that:
7) 11 = c + 5
c = 11 - 5
c = 6
Similarly:
d + 4 = 14
d = 14 - 4
d = 10