11. If a,b,x,ye R,@ #1, is a cube root of unity and (a+b)=x+yo, then (b+aw)' equals: (a) y+x@ 6 (c) -y-xw 12. The value of S = sin- -icos- (c) y+yw (d) -x-ya 2k is: 7 (c)-i (d) i , then value of 1+w+w. +...+ 2k k=1 7 (a) -1 (b) 0 13. If a cos+isin = n n (a) 1+icot (b) 1+i tan 2n 2n (c) 1+i 14. If z = C-{0,-2} is such that log (1/7) | 2-2 |>log (1/7) | z |, then : 15. (a) Re(z) >1 (b) Re(z) 1 60 30 If #1 is a cube root of unity, then zw* -w* is equal to : k=1 k -II* k=1 (a) 0 (b) a (c) 2 (d) None of these (d) Im(z)