we are given
![y=cos(2x)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/q240z7e3awh8syjemxohi23ygn8w0l6fs6.png)
Since, we have to find inverse function
so, we will use following steps
step-1:
Set y=f(x)
It is already there
step-2:
Switch x and y
![x=cos(2y)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/5hurpoxcdasi9tvwnwlzqxxhq7cg96qty6.png)
step-3:
Solve for y
![x=cos(2y)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/5hurpoxcdasi9tvwnwlzqxxhq7cg96qty6.png)
we can take cos^-1 both sides
![cos^(-1)(x)=cos^(-1)(cos(2y))](https://img.qammunity.org/2019/formulas/mathematics/middle-school/ujak2p6p9hhujds998hb7a29dpvm0kv37w.png)
now, we can simplify it
![cos^(-1)(x)=2y](https://img.qammunity.org/2019/formulas/mathematics/middle-school/g04bq0v5k6yvrr1wdvldzgpok0za1jwklt.png)
Divide both sides by 2
![y=(cos^(-1)(x))/(2)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/ex380bvbq83217ifd0hxizagxbyno213sg.png)
so, option-D........Answer