deletions | additions       diff --git a/begin_equation_2_begin_align__.tex b/begin_equation_2_begin_align__.tex  index 4ed1168..81de10f 100644  --- a/begin_equation_2_begin_align__.tex  +++ b/begin_equation_2_begin_align__.tex 
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&= \frac{\partial u}{\partial y} \cdot \frac{\partial u}{\partial x} + u \frac{\partial^2 u}{\partial x \partial y}   = \frac{\partial}{\partial y}\left[ \left( - \frac{\partial \zeta}{\partial y} \right) \cdot \frac{\partial}{\partial x} \left( -\frac{\partial \zeta}{\partial y} \right) \right] = \\  %newline   &= \left(\frac{\partial^2 \frac{\partial^2  \zeta}{\partial y^2} \right) \cdot \left(\frac{\partial^2 \zeta}{\partial x \partial y}\right)  \\ %newline  \frac{\partial}{\partial x}: \;  \frac{\partial v}{\partial t}