I have written the following matrix on Latex:
However, I would like the different elements to be aligned vertically, i.e.:
I have been unable to accomplish this. My code is the following:
\[\phi_1(\mathbf{x}) =
\left(
\begin{array}{l}
x_1^2
\\
\sqrt{2}x_1x_2
\\
x_2^2
\end{array}
\right)\]
Do you know how could I fix this?