Here,    z =
Let       z =                                         ...(1)
                                                        ...(ii)
and                                                                       ...(iii)

Squaring and adding (ii) and (iii), we get
 
             r² = 4                            r = 2
From (ii),         
From (iii),             
since both are positive

∴      lies in 1st quadrant

∴    

Putting in (i), we get 
Which is the required polar form.
Hence,