\begin{equation}
  \left\{
  \begin{aligned}
    f_1(u) &= f(u, 1) = 0.5\, (6u - 2)^2\sin(12u - 4) + 10\, (u - 0.5),\\
    f_2(u) &= f(u, 2) = (6u - 2)^2\sin(12u - 4) + 10,
  \end{aligned}
  \right.
\end{equation}
