Put u = 2x4 + 1 and v = sin u

So y = 3v3

`(dy)/(dx) =(dy)/(dv)(dv)/(du)(du)/(dx)`

`=[9v^2][cos u][8x^3]`

`=[9\ sin^2u][cos(2x^4+1)][8x^3]`

`=72x^3sin^2(2x^4+1)cos(2x^4+1)`