Вот так правильнее будет:
{$N+}
Program Sm;
uses crt;
var x,t,F:Single;
const
a=0.7;
step=0.3;
begin
clrscr;
x:=1;
writeln ('x':3,'t':9,'F(x,t)':13);
while (x <= 2) do begin
t:= 1;
while (t <= 2) do begin
F:=a*x+sin(a*t)/sqrt(2*t+exp(-0.5*x*ln(exp(1))));
writeln (x:3:3, t:9:3, F:9:3);
t:=t+step;
end;
x:=x+step;
end;
readln;
end.