Choose the correct equation(s) for finding the nth roots of a complex number from the list below. Note: there may be more than one correct answer. of Select one or more: O a. r" (cos(no) + isin(no)) O b. Vr(cos( 9+2xk )+ isin( 9+2nk n n Oc. Vr(cos( +2n ) 27 )k + isin( + 27 ) k) O d. rT (cos ( 9+2nk ) + isin( 9+2nck n )) n