I wanna to separate a long equation in an array environment, as it shows in the following graph: Place the right part of || to the below of =.

enter image description here


\[ \Delta P_k^{ij} \; \text{is} \; \left\{ 
  \begin{array}{l l}
    \text{known} & \text{if $\Delta P_k=\bf{0}$}\\
    \bf{0} & \text{if $\Delta P_k=-(I-K_k^i H_k^i)( F_{k-1} P^{ij}_{k-1} F^T_{k-1}+Q_{k-1})(I-K_k^j H_k^j)^T$ }\\
    \text{unknown} & \text{otherwise}.
  \end{array} \right.\]
  • 2
    use the aligned environment from amsmath with the [t] option. Aug 21, 2015 at 14:23

1 Answer 1


Just an extension to Barbaras comment

Note I've replaced \bf as (1) it should not be used, (2) does not take arguments


\[ \Delta P_k^{ij} \; \text{is} 
    \text{known} & \text{if $\Delta P_k=\mathbf{0}$}\\
    \mathbf{0} & \text{if $
        \Delta P_k={}&-(I-K_k^i H_k^i)( F_{k-1} P^{ij}_{k-1}
        &+Q_{k-1})(I-K_k^j H_k^j)^T
      $ }\\
    \text{unknown} & \text{otherwise}.

enter image description here

  • Adding {} after F_{k-1} and Q_{k-1} would lower the subscript terms, making them line up with the other subscript terms in the formula.
    – Mico
    Aug 21, 2015 at 14:33
  • Perhaps writing `(K^i_k H^i_k - I)' reads nicer than '-(I - K^i_k H^i_k)'. It also simplifies the expression slightly. I'd also add one or two quads before the plus symbol or introduce a nicer break, e.g. at the multiplication level.
    – user10274
    Aug 21, 2015 at 14:34
  • Feel free to update the answer
    – daleif
    Aug 21, 2015 at 14:47

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