What is the value of Cos(2Cos^-1x+Sin^-1x) at x=1/5?

cos^-1x + sin^-1x = pi/2   ............1                   (identity)

cos(2cos^-1x+sin^-1x) = cos[(cos^-1x+sin^-1x) + cos^-1x]

=cos[pi/2 + cos^-1x]                             (by using eq 1)

(    we know , cos[pi/2+A] = -sinA   )

=-sin[cos^-1x]

=-sin[sin^-1(1-x²)^1/2]                              (cos^-1x = sin^-1(1-x²)^1/2  )

=-(1-x²)^1/2 

at x = 1/5

=-(2root6)/5