Find the value of `cos((2pi)/5).cos(pi/5)`

Find the value of cos(2 pi)/(7)+cos(4 pi)/(7)+cos(6 pi)/(7)

Find the value of 2cos((5 pi)/(12))cos((pi)/(12)) and 2sin((5 pi)/(12))cos((pi)/(12))

Find the value of (cos(2 pi))/(7)(cos(4 pi))/(7)(cos(6 pi))/(7)

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

The value of cos((pi)/(5))+cos((13 pi)/(5)) is equal to

Find the value of 2cos^(3)((pi)/(7))-cos^(2)((pi)/(7))-cos((pi)/(7))

If the value of cos((2 pi)/(7))+cos((4 pi)/(7))+cos((6 pi)/(7))+cos((7(pi)/(7)))=-(l)/(2) Find the value of l

The value of cos((pi)/(15))cos((2 pi)/(15))cos((4 pi)/(15))cos((8 pi)/(15))=

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