I'm a bit stuck on this problem.
I'm assuming using the substitution $u = 2 + 6x^3.$ And I can find du from there. But I'm stuck on how to take the integral of sin(u).
I would really appreciate it if someone can walk me through this problem step by step.
Here is where I'm stuck:
In my problem what value is a?
$$\int 90x^2\sin(2+6x^3)dx=\int5\sin u du=-5\cos u+C=-5\cos(2+6x^3)+C$$