How do you make parentheses match height when they're split between lines in LaTeX math

Question

Consider the following example

\begin{equation}
    \begin{split}
        f = & \left( \frac{a}{b} + \right. \\
                   & \left. c \right) + d 
    \end{split}
\end{equation}

In the result, the left parenthesis on the first line is very large, because of the fraction inside. In the second line, since there is no fraction, the parenthesis is small. How can I make the one on the second line match the one on the first line in height.

Answer 1

Oh. It's the \phantom{} command

\begin{equation}
    \begin{split}
        f = & \left( \frac{a}{b} + \right. \\
                   & \left. \phantom{\frac{a}{b}} c \right) + d 
    \end{split}
\end{equation}

Answer 2

You can also use \big( \big) to set the size specifically.

The order goes (, \big(, \Big(, \bigg(, \Bigg( for increasing bigness.