Question

I am missing something in my substitution of integrals. For example:
Integral of 5x^2cos(x^3)dx
u=x^3 du=3x^2dx x^2dx=1/3du.
I don't understand where you get the 1/3du.

Answer 1

\[u=x ^{3} = du/dx=3x ^{2} = du/3=x ^{2}dx\]
You move the 3 from the right side of the equation to the left hand by dividing with 1/3.
You're then left with du/3 = x^2dx

Answer 2

If you dont understand what I meant, I'll try to explain further. :)

Answer 3

Thanks I appreciate that!

Answer 4

Good, glad I could help.