`cospi/5+cos(2pi)/5+cos(6pi)/5+cos(7pi)/5=0`

The value of cos(pi)/(5)cos.2(pi)/(5)cos4(pi)/(5)cos8(pi)/(5)=

If the value of "cos"pi/15"cos"(2pi)/15"cos"(3pi)/15"cos"(4pi)/15"cos"(5pi)/15"cos"(6pi)/15"cos"(7pi)/15 is (1)/(2^(k)) , then which of the following is true ?

Solve cos(pi/9)+cos(pi/3)+cos((5pi)/(9))+cos((7pi)/(9)) ?

The value of 2(cos pi/11 + cos(3pi)/11 + cos(5pi)/11 + cos(7pi)/11 + cos(9pi)/11) is……….

cos.(2pi)/(7)+cos.(4pi)/(7)+cos.(6pi)/(7)

Prove that: (cos pi)/(5)(cos(2 pi))/(5)(cos(4 pi))/(5)(cos(8 pi))/(5)=(-1)/(6)

Which of the following is/are the value of "cos"[1/2cos^(-1)(cos(-(14pi)/5)]? cos(-(7pi)/5) (b) sin(pi/(10)) cos((2pi)/5) (d) -cos((3pi)/5)

What is the value of cos(pi//9)+cos(pi//3)+cos(5pi//9)+cos(7pi//9) ?