# runaway argument with fraction

I am trying to write the following equation:

$$\text{N_R} \text{x} (\text{\Delta\sigma_R})^m = 2 \text{x} {10^6} \text{x} (\text{\Delta\sigma_C})^m with m = 3 for \text{N} \leq 5 \text{x} {10^6} \text{N_R} \text{x} (\text{\Delta\tau_R})^m = 2 \text{x} {10^6} \text{x} (\text{\Delta\tau_C})^m with m = 5 for \text{N} \leq 5 \text{x} {10^6} where \text{\Delta\sigma_D} = \text{\frac{2}{5}^{\frac{1}{3}} \text{x} \text{\Delta\sigma_C} = 0.7368 \text{x} \text{\Delta\sigma_C} is the constant amplitude fatigue limit$$


But getting error as:

Runaway argument?
{$\frac{2}{5}^{\frac{1}{3}$} \text{x} \text{$\Delta\sigma_C$} =\ETC.
! Paragraph ended before \text@ was complete.
\par


• Welcome to TeX.SX! Why do you use $ inside a math mode environment? This is not necessary. – TeXnician Apr 28 '17 at 4:31 • Welcome, it seems that this is meant for different lines. You cannot do that with equation. Also, i think all your uses of \text and inline math are wrong. – Johannes_B Apr 28 '17 at 4:46 • To give a direct answer, the problem lies in the third line, replace \text{$\frac{2}{5}^{\frac{1}{3}$} by \text{$\frac{2}{5}^{\frac{1}{3}}$}. Note the double braces before the second $. Not that I would recommend typesetting your equation this way. – Troy Apr 28 '17 at 5:14

You might be looking for the following, but i am really not sure.

\documentclass{article}
\usepackage{mathtools}
\begin{document}
\begin{align}
N_R \times (\Delta\sigma_R)^m &= 2 \times {10^6} \times (\Delta\sigma_C)^m
&&\text{with~}  m = 3 \text{~for~} N\leq 5 \times {10^6}\\
N_R \times (\Delta\tau_R)^m &= 2 \times {10^6} \times (\Delta\tau_C)^m
&&\text{with~}  m = 5 \text{~for~} N \leq 5 \times {10^6}
\end{align}
where $\Delta\sigma_D = \left(\frac{2}{5}\right)^{\frac{1}{3}} \times \Delta\sigma_C = 0.7368 \times \Delta\sigma_C$
is the constant amplitude fatigue limit
\end{document}

• Thank you so much Sir! But my problem is not in 1st two equations but after "where \text..... – Sitesh Singh Apr 28 '17 at 5:09
• What exactly is your problem? – Jürgen Apr 28 '17 at 5:11
• Dear @Sitesh, your code is full of problems. I recommend to read an introduction to LaTeX before doing any more work. It will be a good investment. – Johannes_B Apr 28 '17 at 5:15
• You can copy paste my example and directly compile it. You will be able to see the output directly. – Johannes_B Apr 28 '17 at 5:15

I am not quite sure what you really want to get, but this might be another solution.

\documentclass{article}
\usepackage{amsmath}
\usepackage{siunitx}
\begin{document}
$$N_R \times (\Delta\sigma_R)^m = \num{2e6}\times(\Delta\sigma_C)^m$$

with $m = 3 \quad\forall\quad N\leq\num{5e6}$

$$N_R \times (\Delta\tau_R)^m = \num{2e6}\times(\Delta\tau_C)^m$$

with $m = 5 \quad\forall\quad N\leq\num{5e6}$

where

$$\Delta\sigma_D = \Bigl(\frac{2}{5}\Bigr)^{\frac{1}{3}} \times \Delta\sigma_C = 0.7368 \times \Delta\sigma_C$$

is the constant amplitude fatigue limit

\end{document}

• You should be aware that every blank line results in a new paragraph and disrupts the sentence (and the spacing). – Johannes_B Apr 28 '17 at 5:18
• You're right, of course. But this is intended (and as we do not exactly know, what the OP really wants to achieve, this is only a guess). – Jürgen Apr 28 '17 at 5:26
• Thank you soooo much Jurgen Sir!! Hats off to you!! The solution suggested by you is exactly the one I wanted to write.....Really grateful to you... – Sitesh Singh Apr 29 '17 at 11:15