Question

How do you find the integral of `cos(3x) dx`?

Answer 1

I found: `intcos(3x)dx=1/3sin(3x)+c`

Explanation:

Considering:
`intcos(3x)dx=`

we can set `3x=t`

so: `x=t/3`

and: `dx=1/3dt`

The integral becomes:

`int1/3cos(t)dt=1/3sin(t)+c`

going back to `x`:

we know that `t=3x`:

`=1/3sin(3x)+c`