deletions | additions       diff --git a/begin_equation_2_begin_align__.tex b/begin_equation_2_begin_align__.tex  index dbde37e..41ccf62 100644  --- a/begin_equation_2_begin_align__.tex  +++ b/begin_equation_2_begin_align__.tex 
...
u \frac{\partial u}{\partial x}   \to  \frac{\partial}{\partial y} \left( u \frac{\partial u}{\partial x}\right)   &= =  \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   &= \frac{\partial^2 \zeta}{\partial y^2} \cdot \frac{\partial^2 \zeta}{\partial x \partial y }   + \frac{\partial \zeta}{\partial y } \cdot \frac{\partial^3 \zeta}{\partial x \partial y^2}\\