# How to define acos in relation to cos?

Hey,

Does anyone know how to calculate the formula for acos in relation to cos?

We know that cos (∏/3) = 0.5
and acos(0.5) = ∏/3

However, I assumed I could calculate acos(x) in relation to cos(x) as: 1/cos(x).
Well, I assumed wrong :(

Is there any way to do this?

Thanks