deletions | additions       diff --git a/introduction.tex b/introduction.tex  index beea927..517d92b 100644  --- a/introduction.tex  +++ b/introduction.tex 
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\par   Calculando a primeira derivada de $h(x,y,z)$ em rela\c{c}\~ao a $x$ temos:  \begin{equation}  \frac{\partial  h(x,y,z) }{\partial x}  = \sum^{\infty}_{n=0} \sum^{\infty}_{m=0} exp \{ - (k_x^2 +k_y^2)^{1/2} z \}   [ - A_{m} k_x sin ( k_x x) + B_{m} k_x cos ( k_x x) ]  [ C_{n} cos ( k_y y) + D_{n} sin ( k_y y) ]