3

Is it possible to align an equation like this:

enter image description here

I tried this, but:

\begin{align*}
    & u_a(t) &= u_e(t) - u_{R1}(t) \\
    &        &= u_e(t) - R_1 \cdot i_1(t) = u_e(t) - R_1(i_2(t) + i_3(t)) \\
    &        &= u_e(t) - R_1 \cdot i_2(t) - R_1 \cdot i_3(t) \\
    &        &= u_e(t) - R_1 \cdot \frac{u_a(t)}{R_2} - R_1 \cdot C \cdot \ddt[t]{u_a(t)}\\
<=> & u_a(t) + u_a(t) \cdot \frac{R_1}{R_2} + C \cdot R_1 \ddt[t]{u_a(t)} = u_e(t) \\
\end{align*}

enter image description here

2
  • And what is the \dd macro, please?
    – Bernard
    Commented Oct 7, 2014 at 20:28
  • That's just for the derivation fraction df(x)/dx
    – dersimn
    Commented Oct 8, 2014 at 8:21

1 Answer 1

5

For multiple alignments you can use aligned inside align.

\begin{align*}
    & \begin{aligned}
      u_a(t) &= u_e(t) - u_{R1}(t) \\
             &= u_e(t) - R_1 \cdot i_1(t) = u_e(t) - R_1(i_2(t) + i_3(t)) \\
             &= u_e(t) - R_1 \cdot i_2(t) - R_1 \cdot i_3(t) \\
             &= u_e(t) - R_1 \cdot \frac{u_a(t)}{R_2} - R_1 \cdot C \cdot 
    ddt[t]{u_a(t)}\\
    \end{aligned}\\
<=> & u_a(t) + u_a(t) \cdot \frac{R_1}{R_2} + C \cdot R_1 ddt[t]{u_a(t)} = u_e(t) \\
\end{align*}

enter image description here

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