Y=2x+159 that's the answer .
In a positive integers there are twenty whole numbers I hope this help
D is the only one which would make sense :)
From the identity:


the inverse of f is g such that f(g(x))=x,
we must find g(x), such that
![\frac{1}{cos[g(x)]}=x](https://tex.z-dn.net/?f=%20%5Cfrac%7B1%7D%7Bcos%5Bg%28x%29%5D%7D%3Dx%20)
thus,
![cos[g(x)]= \frac{1}{x}](https://tex.z-dn.net/?f=cos%5Bg%28x%29%5D%3D%20%5Cfrac%7B1%7D%7Bx%7D%20)

Answer: b. g(x)=cos^-1(1/x)