Find the range of `f(x)=sin^(-1)x+tan^(-1)x+cos^(-1)xdot`

Explanation

Three vectors are coplanar when their scalar triple product is `0.`

`=> [veca vecb vecc] = 0`

`=>|[1,-1,1],[2,1,-1],[lambda,-1,lambda]| = 0`

`=>[1(lambda-1)+1(3lambda)+1(-2lambda -1)] = 0`

`=>lambda-1+3lambda-2lambda-1 = 0`

`=> 2lambda = 2`

`=>lambda = 1`, for which these three vectors will be coplanar.