`" The exact value of the expression "cos(12 pi/17)+cos(14 pi/17)+2cos(4 pi/17)cos(pi/17)" is "`

The value of the expression cos((pi)/(2)-x)cos((3 pi)/(2)+x)-cos(pi-x)cos(2 pi-x)

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

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

The value of cos(2 pi)/(21)+cos(4 pi)/(21)+cos(6 pi)/(21)+....+cos(20 pi)/(21) is equal to

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

The expression 2"cos"(pi)/(17)*"cos"(9pi)/(17)+"cos"(7pi)/(17)+"cos"(9pi)/(17) simplifies to an integer P. Find the value of P.