### $4.$ For $3$ dimension Graphs

Consider the following equation $(3)$ and conditions:

$$

z$=$x$^\backslash$alpha $\backslash$alpha $$x$+$y$^\backslash$beta $\backslash$beta $$y$+$cos$(\backslash$alpha $$x$+\backslash$beta $$y$)\backslash$:$\backslash$:$\backslash$:$\backslash$:$\backslash$: $(3)$

$$

Here are the first given conditions.

$-$ $$\backslash$alpha $=4$$ and $$\backslash$beta $=3$$

$-$ $$10$x$10$$$,$ $$8$y$8$$$,$ $$$x$=0\mathrm{.}2$$$,$ and $$$y$=0\mathrm{.}5$$$.$

$-$ For drawing a $3$ dimensional surface $($surf$,$ mesh, contour$3$ and so on$)$ of the equation $(3),$ create $x$$,$ $y$$,$ and $z$ data. $($Don$$t draw the $3$ dimensional graph.$)$

$-$ Save $x$$,$ $y$$,$ and $z$ data on $***$EX$1\_16.$dat$***,***$EX$1\_17.$dat$***,$ and $***$EX$1\_18.$dat$***$ respectively.