If for z as real or complex,,then
Putting z = i, where ,
or
Also, putting
or
Putting ,
or
Putting x = 1
Adding (2), (3) and (4), we have
or
Similarly, first multiplying (1) by z and then putting 1,and adding, we get
Multiplying (1) z2 and then putting 1, and adding,
We get