If `(3-tan^(2)""(pi)/(7))/(1-tan^(2)""(pi)/(7))=kcos""(pi)/(7)` then the value of k is

If (3-"tan"^(2)(pi)/(7))/(1-"tan"^(2)(pi)/(7))="k cos" (pi)/(7) then the value of k is

If (3-tan^(2)((pi)/(7)))/(1-tan^(2)((pi)/(7)))=k cos((pi)/(7)) then the value 1-tan^(2)((pi)/(7)) of k is (a) (b)2(c)3(d)4

tan^(-1)("tan"(7pi)/(5))

tan^(-1)(tan""(7pi)/(6))

tan^(-1)(tan((6 pi)/(7)))

tan^(-1)(tan((7pi)/6))

tan^(-1)(tan((-33 pi)/(7)))

2tan^(-1)(tan((7pi)/6))

cos(cos^(-1)cos((8 pi)/(7))+tan^(-1)tan(8(pi)/(7))) has the value equal to -

tan^(-1){tan(-(7 pi)/(8))}