>z = cis(r) = cos(r) + isen(r)>z^n = cis(nr) = cos(nr) + isen(nr)>Sum(cis(kr)) = Sum(z^k) , k = 1 ... n>Sum(z^k) = z + z^2 + z^3 + ... + z^n = z(z^n - 1) / (z - 1) [somatorio >de PG]>Sum(z^k) = cis(r) [ cis(nr) - 1 ] / [ cis(r) - 1 ]>Sum(cis(kr)) = cis(r) [ cis(nr) - 1 ] / [ cis(r) - 1 ] = cis(r) [ cis(nr) - 1 ] * >[ cis(-r) - 1 ] / [ 1 - cis(-r) - cis(r) + 1 ]>cis(r) + cis(-r) = cos(r) + isen(r) + cos(r) - isen(r) = 2cos(r)>Sum(cis(kr)) = [ cis(r)cis(nr)cis(-r) - cis(r)cis(-r) - cis(r)cis(nr) + cis(r) ] / >[ 2 + 2cos(r) ]>Re(Sum(cis(kr))) = Sum(cos(kr))>Im(Sum(cis(kr))) = Sum(sen(kr))>Sum(cis(kr)) = [ cis(nr) - 1 - cis[(n+1)r] + cis(r) ] / 2[1 + cos(r)]>Re(Sum(cis(kr))) = [ cos(nr) - 1 + cos[(n+1)r] + cos(r) ] / 2[1+cos(r)]>Im(Sum(cis(kr))) = [ sen(nr) - 1 - sen[(n+1)r] + sen(r) ] / 2[1+cos(r)]Re(Sum(cis(kr))) = [ cos(nr) - 1 - cos[(n+1)r] + cos(r) ] / 2[1+cos(r)]Im(Sum(cis(kr))) = [ sen(nr) - sen[(n+1)r] + sen(r) ] / 2[1+cos(r)](...)bem,acho q eh issoabração