Math & Science ⇒ referencing a non-existing label in equation

[kalmer]

i use align as in the following example:

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Code, edit and compile here:

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\begin{align}
RH :&= \cfrac{m_w}{m_\text{sat}(w)} = \cfrac{M_w \cdot n_w}{M_\text{sat}(w) \cdot n_\text{sat}(w)} = \cfrac{M_w \cdot \frac{p_w \cdot \cancel{V}}{\cancel{R \cdot T}}}{M_\text{sat}(w) \cdot \cfrac{p_\text{sat}(w) \cdot \cancel{V}}{\cancel{R \cdot T}}} = \frac{p_w}{p_\text{sat}(w)}\\
&= \frac{\frac{W \times p}{W + `r M_w_TO_M_d`}}{p_\text{sat}(w)} = \frac{W \times p}{(W + `r M_w_TO_M_d`) \cdot p_\text{sat}(w)} = \frac{x_w}{x_\text{sat}(w)}|_{T, P}
(\#eq:relative-humidity)
\end{align}
 
 
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Run LaTeX here

Based on this source code, a multi-line equation will be created having two numeric labels on the right-hand side, one for each line. If i want to reference the the equation, i use \@ref(eq:relative-humidity) and that works fine. However, i want to refer the first line, not the second line. How can i do that? i tried the following:

Code: Select all

Code, edit and compile here:

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\begin{align}
RH :&= \cfrac{m_w}{m_\text{sat}(w)} = \cfrac{M_w \cdot n_w}{M_\text{sat}(w) \cdot n_\text{sat}(w)} = \cfrac{M_w \cdot \frac{p_w \cdot \cancel{V}}{\cancel{R \cdot T}}}{M_\text{sat}(w) \cdot \cfrac{p_\text{sat}(w) \cdot \cancel{V}}{\cancel{R \cdot T}}} = \frac{p_w}{p_\text{sat}(w)}\\(\#eq:relative-humidity-ratio-of-pressures)
&= \frac{\frac{W \times p}{W + `r M_w_TO_M_d`}}{p_\text{sat}(w)} = \frac{W \times p}{(W + `r M_w_TO_M_d`) \cdot p_\text{sat}(w)} = \frac{x_w}{x_\text{sat}(w)}|_{T, P}
(\#eq:relative-humidity)
\end{align}
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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Run LaTeX here

That resulted with:

! Package amsmath Error: Multiple \label's: label 'eq:relative-humidity-ratio-of-pressures' will be lost.

[Bartman]

Please expand your example to a complete minimal working example that produces your error message.

A line in the align environment can only be referenced if one \label command precedes the end of the line. In your case the first line would have no label and the second two or multiple, as the error message states.

[Kreuz Elf]

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(\#eq:relative-humidity-ratio-of-pressures)
 
 
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Code: Select all

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(\#eq:relative-humidity)
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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I've not seen this syntax before. Maybe it is a legit variant, but consider using \lable{eq:relative-humidity-ratio-of-pressures}