3

I'm trying to have all my equation aligned to the left of the document instead of the center. I'm trying with flalign but fore some strange reason I get this :

enter image description here

Here is the code :

\documentclass[11pt, french]{article} %article report  book  letter  slides
\usepackage{blindtext}
\usepackage{geometry}
 \geometry{
 a4paper,
 total={170mm,257mm},
 left=20mm,
 top=20mm,
 }
\usepackage[french]{babel}
\selectlanguage{french}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{esint}
\begin{document}
\newcommand{\prt}[2]{\frac{\partial #1}{\partial #2}}

\begin{flalign}
C_x = C_{x_0} + k{C_z}^2 && \
\prt{f}{C_z} = \frac{0.015+\frac{{C_z}^2}{20}-\frac{{C_z}^2}{10}}{\left( 0.015+{C_z}^2 \right)^2}&&\
\prt{f}{C_z} = 0 \Leftrightarrow C_{x_0} + k{C_z}^2 - 2k{C_z}^2 = 0 \Leftrightarrow C_z = \sqrt{\frac{C_{x_0}}{k}} = 0,548 &&\
C_x = 0.015 + \frac{1}{20} * 0.548^2 = 0.03&&\
f = \frac{0.548}{0.03} = 18,26 &&
\end{flalign}


\end{document}

How can I fix my problem?

Azagal258
  • 35

2 Answers2

6

enter image description here

Use [fleqn] to get equations flush left, and use gather not align as you are not aligning on =

\documentclass[11pt, french,fleqn]{article} %article report  book  letter  slides
\usepackage{blindtext}
\usepackage{geometry}
 \geometry{
 a4paper,
 total={170mm,257mm},
 left=20mm,
 top=20mm,
 }
\usepackage[T1]{fontenc}
\usepackage[french]{babel}
\selectlanguage{french}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{esint}
\begin{document}
\newcommand{\prt}[2]{\frac{\partial #1}{\partial #2}}

\begin{gather}
C_x = C_{x_0} + k{C_z}^2  \
\prt{f}{C_z} = \frac{0.015+\frac{{C_z}^2}{20}-\frac{{C_z}^2}{10}}{\left( 0.015+{C_z}^2 \right)^2}\
\prt{f}{C_z} = 0 \Leftrightarrow C_{x_0} + k{C_z}^2 - 2k{C_z}^2 = 0 \Leftrightarrow C_z = \sqrt{\frac{C_{x_0}}{k}} = 0,548 \
C_x = 0.015 + \frac{1}{20} * 0.548^2 = 0.03\
f = \frac{0.548}{0.03} = 18,26 
\end{gather}


\end{document}
David Carlisle
  • 757,742
3

As David Carlisle has already pointed in his answer, you need to specify the option fleqn, either as an option at the document class stage or when loading the amsmath package.

I would keep using an align setup for the five questions in your sample document.

enter image description here

\documentclass[11pt,french,fleqn]{article} 
\usepackage{geometry}
\geometry{a4paper,total={170mm,257mm},left=20mm,top=20mm}
\usepackage{babel}
\usepackage{amssymb}
\usepackage{amsmath}
\newcommand{\prt}[2]{\frac{\partial #1}{\partial #2}}
\usepackage{showframe}
\begin{document}

\begin{align}
C_x &= C_{x_0} + k{C_z}^2  \
\prt{f}{C_z} &= \frac{0.015+C_z^2/20-C_z^2/10}{(0.015+C_z^2)^2}\
\prt{f}{C_z} &= 0 
  \quad\Longleftrightarrow\quad 
  C_{x_0} + k{C_z}^2 - 2k{C_z}^2 = 0 
  \quad\Longleftrightarrow\quad 
  C_z = \sqrt{C_{x_0}/k} = 0.548 \
C_x &= 0.015 + (1/20) \cdot 0.548^2 = 0.03\
f   &= 0.548/0.03 = 18.26 
\end{align}


\end{document}
Mico
  • 506,678