\documentclass[preview,border=1pt]{standalone}
\usepackage{amsmath,amssymb,amsthm}


\begin{document}

\begin{align*}
f(x)+g(x)+h(x) &= \big|\sin x + 2\cos x + 3\sin^2 x + 4\cos^4 x \\
&\hphantom{{}={}} \big|+ 5 \sin^5 x + 6\cos^6 x \\
&= \int_0^x \Big(\big|p(y)\cos y + q(y)\sin^3 y e^y - r(y)\sin y  \\
&\hphantom{{}= \int_0^x \Big(} \big|- s(y) - e^{y^2}\Big)\,dy.
\end{align*}
\end{document}