Strange Underfull \vbox problem [closed]

Question

This is the code:

\[
  \left.
  \begin{aligned}
    K_1 \cos{\theta^{(1)}_4} - K_2 \cos{\theta^{(1)}_2} + K_3 & = \cos(\theta^{(1)}_4 - \theta^{(1)}_2) \\
    K_1 \cos{\theta^{(2)}_4} - K_2 \cos{\theta^{(2)}_2} + K_3 & = \cos(\theta^{(2)}_4 - \theta^{(2)}_2) \\
    K_1 \cos{\theta^{(3)}_4} - K_2 \cos{\theta^{(3)}_2} + K_3 & = \cos(\theta^{(3)}_4 - \theta^{(3)}_2)
  \end{aligned}
  \right\}
\]

It shows me:

Underfull \vbox (badness 10000) has occurred while \output is active []

But if I comment any equation line, so there are 2 of the 3, any message is shown.

Any advice, please?

Answer 1

The code by itself has nothing wrong. You are unlucky enough that the display falls near the end of a page and there's not sufficient space to accommodate it. Thus LaTeX has no choice rather than moving the entire display (and also one line of text before it) to the next page.

In your case the display is just a tad too big for staying in the page, so moving it to the next page produces a "page too empty".

There's not much that one can do "automatically". Leave the decision for the final revision of the document, when you'll be sure that the text won't change; that's the time for fixing pagination problems like this. In many cases, changes to the text preceding that display might help to "gain a line" so that the display will fit.