Overbrace/underbrace without extending brackets/parentheses

Question

I'm using \overbrace to explain a part of an equation, like this:

\begin{align}
a\left[\frac{d\cos y}{e} + \overbrace{\frac{b\sin x}{c}}^{\text{second bit}}\right]
\end{align}

But the overbrace increases the height of the brackets unnecessarily:

Really, what I'd like is for the height of the brackets to be unrelated to the overbrace, like this:

Is this possible?

Answer 1

You can often literally smash the part which fiddles with your desired height :)

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
a\left[\frac{d\cos y}{e} + \smash{\overbrace{\frac{b\sin x}{c}}^{\text{second bit}}}\right]
\end{equation}
\end{document}

This comes closer to the posted intended output than David's answer, concerning the size of the brackets. \smash is a macro defined in both plain TeX and the LaTeX kernel. It reduces the height of its arguments to zero.

Answer 2

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
a\Bigl[\frac{d\cos y}{e} + \overbrace{\frac{b\sin x}{c}}^{\text{second bit}}\Bigr]
\end{equation}
\end{document}