deletions | additions       diff --git a/untitled.tex b/untitled.tex  index eaf3eda..80d5697 100644  --- a/untitled.tex  +++ b/untitled.tex 
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$$  {{\partial \Phi } \over {\partial {X_{\rm{P}}}}} =   \begin{cases}  - 78.9{\text{, 78.9\text{,  if }, }  {X_{\rm{P}}} < 0.34\\ - 628.3{\text{, 628.3\text{,  if }, }  {X_{\rm{P}}} \ge 0.34 \end{cases}  \label{eq:comp}  $$