The integral $$\int {3 \sin(x) \cos(x)}\, dx$$ can be evaluated in four different ways:

(1) The substitution $u=\cos(x)$

(2) The substitution $u=\sin(x)$

(3) The identity $\sin(2x) = 2 \sin(x) \cos(x)$

(4) Integration by parts

Use any of these methods to evaluate the integral.

Note: Use an upper-case "C" for the constant of integration.