Efficient Simplification of cos(sin^{-1}(9x))

[astr0]

I need to simplify this expression. How do I go upon that? $$cos(sin^{-1}(9x))$$

 

[Mark44]

I need to simplify this expression. How do I go upon that? $$cos(sin^{-1}(9x))$$

What have you tried? Before we can help you, you need to have made an effort at solving the problem for yourself.

 

[SammyS]

What have you tried? Before we can help you, you need to have made an effort at solving the problem for yourself.

I agree with Mark!