`underset(r=1)overset(n-1)(sum)cos^(2)""(rpi)/(n)` is equal to

underset(r=0)overset(n)(sum)sin^(2)""(rpi)/(n) is equal to

underset(r=0)overset(n)(sum)sin^(2)""(rpi)/(n) is equal to

sum_(r=1)^(n-1)cos^(2)""(rpi)/(n) is equal to

Prove that the value of underset(r=0)overset10sum cos^3((rpi)/3) is equal to -1/8

sum_(r=0)^(n) sin^(2)""(rpi)/(n) is equal to

underset(n to oo)lim" " underset(r=2n+1)overset(3n)sum (n)/(r^(2)-n^(2)) is equal to

If k=underset(r=0)overset(n)(sum)(1)/(.^(n)C_(r)) , then underset(r=0)overset(n)(sum)(r)/(.^(n)C_(r)) is equal to

underset(r=1)overset(n)(sum)r(.^(n)C_(r)-.^(n)C_(r-1)) is equal to

underset(r=1)overset(n)(sum)r(.^(n)C_(r)-.^(n)C_(r-1)) is equal to

underset(r=1)overset(n)sum ( r )/(r^(4)+r^(2)+1) is equal to