Question

plz.......answer urgent easy​

Answer 1

from k= 0 to 8 e^i( 2kpie/9) = 0

as they are 9 th roots of unity

for k= 0 its 1 , cos0 = 1

So its -1

Answer 2

Answer:

from k= 0 to 8 e^i( 2kpie/9) = 0

as they are 9 th roots of unity

for k= 0 its 1 , cos0 = 1

So its -1