Find the value `"cos"(pi)/(11)+"cos"(3pi)/(11)+"cos"(5pi)/(11)+"cos"(7pi)/(11)+"cos"(9pi)/(11)`

Find the value of "cos"^(2)(pi)/(16)+"cos"^(2)(3pi)/(16)+"cos"^(2)(5pi)/(16)+"cos"^(2)(7pi)/(16) .

Find the value of sin((-11pi)/3)

One of the value of ("cos"(pi)/(6) +i "sin"(pi)/(6))^((1)/(2)) + ("cos"(pi)/(6)- i "sin"(pi)/(6))^((11)/(2)) is

find the value of cos^-1cos((7pi)/3)

Prove that (1+"cos"(pi)/(8))(1+"cos"(3pi)/(8))(1+"cos"(5pi)/(8))(1+"cos"(7pi)/(8))=(1)/(8) .

Evaluate cos^2(pi/8)+cos^2((3pi)/8)

Evaluate cos^2(pi/8)+cos^2((3pi)/8)+cos^2((5pi)/8)+cos^2((7pi)/8)=2

Prove that 2cos(pi/13)cos((9pi)/13)+cos((3pi)/13)+cos((5pi)/13)=0

The value of [ cos ""(pi)/(8) + isin ""(pi)/(8) ]^(4) is