Angles of a parallelogram
Case 1
We have that the diagonals of a parallelogram cut in halfs all the angles. Then, in this case:
because both angles of the sides of the diagonal may be equal.
Then
m∠DEC = 71º
m∠DFE = 21º
Since the opposite angles of the parallelogram are equal too, we have:
And then,
m∠ECD = 71º
Since
71º + 71º = 142º
and
21º + 21º = 42º
then
m∠CDE = 42º
Answers
Then, the answers are:
m∠DEC = 71º
m∠CDE = 42º
m∠ECD = 71º
m∠DFE = 21º
Case 2
If we consider that
m∠FED = 134º
then, we have that