\begin{eqnarray}[\{]
$$\frac{\partial{x_i}}{\partial{q_j}} = \sum_{j = 1}^{n}\frac{\partial{x_i}}{\partial{q_j}} $$ \\
$$\frac{\partial{y_i}}{\partial{q_j}} = \sum_{j = 1}^{n}\frac{\partial{y_i}}{\partial{q_j}} $$ \\
$$\frac{\partial{z_i}}{\partial{q_j}} = \sum_{j = 1}^{n}\frac{\partial{z_i}}{\partial{q_j}} $$
\end{eqnarray}
I don't see the fault here. Could you guys please help me ??
eqnarray
is very wrong ... remove all$
and than try again. if you will provide complete but small document we can easily show how to correct type your system of equations. – Zarko Feb 13 '18 at 15:19eqnarray
is considered obsolete. try to use environment fromamsmath
package. – Zarko Feb 13 '18 at 15:36eqnarray
vsalign
. – Werner Feb 13 '18 at 15:37