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\begin{equation}
g(f,t) = \begin{cases}
         \bigl{b^Nt^N^-^1e^2^\pi^b^t cos(2\pi ft),  \text{t\geq 0;}\\
         0 \text{ $ otherwise $}
         \end{cases}
\end{equation}
3
  • 1
    (1) welcome, (2) please post a full minimal example that others can copy and test as is. You are doing many mistakes here. \bigl{ should be \bigl\{ (but is it needed), the first \text needs math mode inside it (the contents is math, the other one does not (its text) and you need \\ to break the line inside cases env
    – daleif
    May 15, 2017 at 6:05
  • Welcome to TeX. SE! Your code has to much errors to be useful (see daleif comment). Please provide image of it written by hand.
    – Zarko
    May 15, 2017 at 6:25
  • The string b^Nt^N^-^1e^2^\pi^b^t cannot possibly be correct. Please edit and fix your code.
    – Mico
    May 15, 2017 at 6:30

1 Answer 1

7

I think that you mean something like this:

\documentclass{amsart}
\begin{document}

\begin{equation}
g(f,t) = \begin{cases}
           b^Nt^{N^{-1}}e^{2\pi b^t}\cos(2\pi ft),&  \text{if }t\geq 0,\\
           0,& \text{otherwise.}
         \end{cases}
\end{equation}

\end{document}

which produces:

enter image description here

Note, in particular:

  • you don't need to add \bigl\{ because part of the point of the the cases environment is that it adds the large left brace around the equations for you
  • use & to separate the branches of the functions and the text that describes them
  • to create superscripts use brackets to group the elements in the exponent: so e^{2\pi t} is, mathematically, the same as \exp(2\pi t)
  • use \text{...} to print text inside equations. In particular, gets you out of math-mode...your expression \text{ $ otherwise $} is wrong in so many ways: \text{otherwise} is what you want, Also, be careful with spaces because \text{ otherwise } will print otherwise
  • if you want to type braces in LaTeX then you need to use \{ and \}, rather than { and }
  • many standard functions like cos, sin, exp, ... have their own macros: \cos, \sin, \exp, .... It looks much better if you use these because, otherwise, TeX will typeset cos etc so that it looks like c*o*s
4
  • I'd probably use \text{if $t\geq0$}, just because the entire text is the comment. Better semantics
    – daleif
    May 15, 2017 at 7:11
  • @daleif Yes, I agree/ In this case it isn't so clear but if the condition was \text{if $t\ge0$ and $f<0$}, it your approach is definitely better. This said, I normally use \begin{cases*}...\end{cases*} from mathtools, which does this implicitly, but I didn't want to mention this here because the OP has enough other things to worry about.
    – user30471
    May 15, 2017 at 7:17
  • Please, fix the cosine
    – egreg
    May 15, 2017 at 7:17
  • 2
    it also can be (more probably) g(f,t) = \begin{cases} b^N t^{N-1}\mathrm{e}^{2\pi b t} \cos(2\pi f t), & \text{if }t\geq 0,\\ 0, & \text{otherwise.} \end{cases} :)
    – Zarko
    May 15, 2017 at 7:29

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