sum_(K=1)^(3)cos^(2)[(2K-1)(pi)/(12)]=

The value of 1+sum_(k=0)^(12){(cos((2k+1)pi))/(13)+i(sin((2k+1)pi))/(13)}

The value of 1+sum_(k=0)^(14) {cos((2k+1)pi)/(15) - isin((2k+1)pi)/(15)} , is

The value of 1+sum_(k=0)^(14) {cos((2k+1)pi)/(15) - isin((2k+1)pi)/(15)} , is

If sum_(r=1)^(k)cos^(-1)beta_(r)=(k pi)/(2) for any k>=1 and A=sum_(r=1)^(k)(beta_(r))^(r) then lim_(x rarr A)((1+x)^((1)/(3))-(1-2x)^((1)/(4)))/(x+x^(2)) is equal to

The value of sum_(K=1)^(2015)cos((2kpi)/(13))(i-tan((2k pi)/(13)) is a) -1 b) 0 c) 1 d) 2

The value of 1+sum_(k=0)^14{(cos)((2k+1)pi)/(15)+(isin)((2k+1)pi)/(15)} is

Prove that sum_(k=1)^(n-1)(n-k)(cos(2k pi))/(n)=-(n)/(2) wheren >=3 is an integer