Let $R$ be the region bounded by $y=\sin x$ and $y=\cos x$ between $x=-\pi / 4$ and $x=3 \pi / 4 .$ Find the volume of the solid obtained when $R$ is revolved about $x=-\pi / 4$. Hint: Use cylindrical shells to write a single integral, make the substitution $u=x-\pi / 4,$ and apply symmetry properties.