# Math Help - Intergrals Problems

1. ## Intergrals Problems

1. Finding indefinite integrals (without the integration constant).
????

How come the answer is not (cosx)(sinx)(x)??
What does (without the integration constant) mean?

2. NEvermind, i already solved number 2. Just need help on 1 thanks.

3. remember if the integral of f is F then F ' = f

So differentiate cos(x)sin(x)*x and you won't get sin(x)cos(x)

Now I think you are thinking "integral of fg = integral of f times integral of g"

but this isn't correct.
There is no product rule for integration
But even for derivatives (fg) ' is not simply f ' g' is it ?

There are 2 ways to solve your integral

1, using u substitution let u = sin(x) or u = cos(x) either will work here

2.use the identity sin(x)cos(x) =1/2sin(2x) and use u = 2x