deletions | additions       diff --git a/begin_equation_2_begin_align__.tex b/begin_equation_2_begin_align__.tex  index 0ff2ca7..5cf9803 100644  --- a/begin_equation_2_begin_align__.tex  +++ b/begin_equation_2_begin_align__.tex 
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\to  \frac{\partial}{\partial x} \left( u \frac{\partial v}{\partial x}\right)   = \frac{\partial u}{\partial x} \cdot \frac{\partial v}{\partial x} + u \frac{\partial^2 v}{\partial x^2}   &= \frac{\partial}{\partial x}\left[ \left( - \left(-  \frac{\partial \zeta}{\partial y} \right) \cdot \frac{\partial}{\partial x} \left( -\frac{\partial \frac{\partial  \zeta}{\partial y} x}  \right) \right] = \\ %newline   &= -  \frac{\partial^2 \zeta}{\partial y^2} x \partial y}  \cdot \frac{\partial^2 \zeta}{\partial x \partial y x^2  } + -  \frac{\partial \zeta}{\partial y } \cdot \frac{\partial^3 \zeta}{\partial x \partial y^2}\\ x^3 }\\  \end{align*}  \end{equation}