[Tex/LaTex] How to write a function (piecewise) with bracket outside

bracketsequationsmath-mode

How to write this Piecewise function using LaTeX?

Piecewise Function

I tried

$
\begin{array}{cc}
  \{ & 
    \begin{array}{cc}
      0 & x\leq 0 \\
      \frac{100-x}{100} & 0\leq x\leq 100 \\
      0 & 100\leq x
    \end{array}
\end{array}
$

but it didn't work perfectly, the bracket "{" looks small, see:

Piecewise Function with LaTeX

Best Answer

This situation is exactly what the cases environment from the amsmath package was designed for. If you put

\usepackage{amsmath}

in your preamble then you can wite

\[ \begin{cases} 
      0 & x\leq 0 \\
      \frac{100-x}{100} & 0\leq x\leq 100 \\
      0 & 100\leq x 
   \end{cases}
\]

to adapt your example with the correct size bracket.


As for not being able to use TeX-like syntax to write equations on this site: this is a deliberate choice. Most of the time we actually want to talk about the TeX source here rather than the equations (or whatever) it produces; and there are times when it could be actively confusing to have a TeX-like process to produce images that isn't actually TeX (in its full, Turing-complete, confusing glory...)

(See the discussion on meta for more on this, if you're interested.)

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