Firstly, we need the equation to be in terms of one cosh argument if possible, which can be done by the identity cosh 2x = 2cosh2x - 1. Upon substitution and simplification we get 6cosh2
f(x) = x3 + 3x V = π ∫ (f(x)2) dx V = π ∫02 (x3 + 3x)(x3 + 3x) dx V = π ∫02 (x6 + 6x4