alph0 = 15*π/180;
gamm0 =  .13;
v0 = 155;
v0x = v0*Cos[alph0];
v0z=v0*Sin[alph0];
g = 9.80;
tR = 2*v0z/g;
%
XX[t_] = v0x*t;
Xdrag[t_] = 
            v0x*(1 - Exp[-gamm0*t])/gamm0;
ZZ[t_] = v0z*t -  .5*g*t^2;
Zdrag[
              t_] = -g*
                t/gamm0 + (gamm0*v0z + g)*(1 - Exp[-gamm0*t])/
                  gamm0^2;
ParametricPlot[{{XX[t], ZZ[t]}, {Xdrag[t], 
                Zdrag[t]}}, {t, 0, tR}, PlotLabel -> "Projectile", 
            AspectRatio -> 1, AxesLabel -> {"x", "z"}, 
            PlotRange -> {0, Automatic}, 
            PlotStyle -> {Dashing[{1, 0}], Dashing[{ .001,  .01}]}];