7" If "pi<=x<=2 pi," then "cos^(-1)(cos x)" is equal to "

Find the value of cospi/7+cos(2pi)/7+cos(3pi)/7+cos(4pi)/7+cos(5pi)/7+cos(6pi)/+cos(7pi)/7

Show that : "sin" 2(pi)/(7)+ "sin"(4pi)/(7)-"sin" (6pi)/(7) =4 "sin" (pi)/(7) "sin" (2pi)/(7) "sin" (3pi)/(7)

Prove that, "cosec" (2pi)/7 + "cosec" ( 3pi)/7 = "cosec" pi/7

The value of cos""(pi)/(7)+cos""(2pi)/(7)cos""(3pi)/(7)+cos""(4pi)/(7)+cos""(5pi)/(7)+cos""(6pi)/(7)+cos""(7pi)/(7) is

The value of cos(pi/7)+cos((2pi)/7)+cos((3pi)/7)+cos((4pi)/7)+cos((5pi)/7) +cos((6pi)/7)+cos((7pi)/7) is