Range of f(x)= cos-1x + 2sin-1x +3tan-1x is :

Use this to reduce the function
cos-1x + sin-1x = pi/2.
after using this the function will just be “pi/2 +sin-1x +3tan-1x” and we can see both are monotonous fucnctions and that too increasing soo put in the values from maxima to minima to get in the answers for the range