When I plug
$$\int_0^\infty |\sin x|e^{-x}dx$$
into symbolab, it tells me the first step is to find the equivalent expression for the integrand at $0\leq x \leq \infty$. It says this expression is $\sin (x) e^{-x}dx$.
I don't understand this because on $0\leq x \leq \infty$, $\sin x$ is not just zero or a positive number. It can be negative so you can't just remove the absolute value bars.