If `tan^(- 1)\ 1/4+tan^(- 1)\ 2/9=1/2cos^(- 1)x` then `x` is equal to

tan^(-1)((2x-1)/(10))+tan^(-1 )(1/(2x))=(pi)/(4) , then x is equal to

2tan ^ (- 1) (cos x) = tan ^ (- 1) (2cos ecx)

if tan^(-1)(1/x)+cos^(-1)(2/sqrt5)=pi/4 then x equals

if tan^(-1)(1/x)+cos^(-1)(2/sqrt5)=pi/4 then x equals

The value of 2tan^(-1)(cos ec tan^(-1)x-tan cot^(-1)x) is equal to (a)cot ^(-1)x( b ) (cot^(-1)1)/(x) (c)tan ^(-1)x (d) none of these