Write the complex number in the polar form.

Let    z = i -1 = -1 + i =  r()                                      ....(i)
         r cos   = - 1                                                                  ...(ii)
             r sin   =   1                                                                  ...(iii)
Squaring and adding (ii) and (iii) we get
                          r²   = 2                     r =

∴ From (ii) and (iii).
                      
                                   

∴  

   
  
      
 
 
 Which is the  reequired polar form.