[Tex/LaTex] How to make equations the same size

Question

When I write an equation using the simple \[ and \], it comes out to the correct size, with the fractions bulging above and below the lines and the parentheses surrounding them.

But when I use the {array} environment, the equations become squished, and all the fractions are squeezed into the line.

How can I get the array environment to look the same as if I were typing an individual equation?

\[ I(a;b)=I\left(\frac{1}{a};\frac{1}{b}\right)\]

is what I want the following array to look like:

\[\begin{array}{rcl}

I\left(a;\frac{1}{a}\right) & = & I\left(\frac{1}{a};a\right) \\

I\left(a;\frac{1}{a}\right) & = & -I\left(a;\frac{1}{a}\right) \\

\hbar I\left(a;\frac{1}{a}\right) & = & 0

\end{array}\]

Answer 1

This is what you may need actually.

\documentclass{article}
\usepackage{mathtools}
\begin{document}
\begin{align*}
I\left(a;\frac{1}{a}\right) &=  I\left(\frac{1}{a};a\right) \\
I\left(a;\frac{1}{a}\right) &=  -I\left(a;\frac{1}{a}\right) \\
\hbar I\left(a;\frac{1}{a}\right) &= 0
\end{align*}
\end{document}