" 12."cos^(-1){(1)/(sqrt(2))(cos(7 pi)/(5)-sin(2 pi)/(5))}" is equal to "

cos^(-1){(1)/(sqrt(2))(cos(7 pi)/(5)+sin(2 pi)/(5))} is equal to (A) (23 pi)/(20) (B) (13 pi)/(20) (C) (3 pi)/(20) (D) (7 pi)/(20)

cos^(-1) (1/sqrt2 (cos ((7pi)/5)-sin((2pi)/5))) is equal to (a pi)/b where a,b in N and a is prime then (b-2a)=

if cos^(-1)((1)/(sqrt(2))(cos((7pi)/(5)-sin((2pi)/(5)))=(ppi)/(q) (where p,q are in lowest form), then value of (q-p) is

if cos^(-1)((1)/(sqrt(2))(cos((7pi)/(5))-sin((2pi)/(5)))=(ppi)/(q) (where p,q are in lowest form), then value of (q-p) is

cos^(-1)((cos(7 pi))/(5)) is equal to

cos ^(-1) [ cos ((7pi)/(5))] is equal to

sin^(-1)(cos((5pi)/4)) is equal to

sin^(-1)(cos((5pi)/4)) is equal to

cos((pi)/(15))cos((2 pi)/(15))cos((pi)/(5))cos((4 pi)/(15))cos((2 pi)/(5))cos((7 pi)/(15)) is equal to