паскаль

[Александр ето я]

подскажите как сделатьпроверку деления на ноль(не могу придумать, хоть убейте). вот код проги:
uses
crt;

const
st1='1/sin(x)';
st2='1/cos(x)';

type
Func=function(x:real):real;

var
first,step,last:real;
j:integer;
fil:text;
path:string;

{$F+}
Function F(c:real):real;
begin
F:=1/sin(c);
end;

Function M(c:real):real;
begin
M:=1/cos(c);
end;
{$F-}

procedure Mnogo(var f:text; k,st,l:real; R,Q:func;st1, st2:string); {Vivod na ekran}

var
s:real;

begin
writeln('Expression':20,'|',st1:20, '|',st2:20,'|');
for j:=1 to 63 do
begin
write('-');
write(f,'-');
end;
writeln;
writeln(f,'');
writeln(f,'Expression':20,'|',st1:2 0,'|',st2:20,'|');
s:=k;
repeat
if (l-s)<st then
s:=l;
writeln(s:20:4,'|',R(s):20:2,'|',Q( s):20:2,'|');
writeln(f,s:20:4,'|',R(s):20:2,'|', Q(s):20:2,'|');
s:=s+st;
until s>l;
for j:=1 to 63 do
begin
write('-');
write(f,'-');
end;
close(f);
end;

Begin
clrscr;
writeln('Type the first value of your argument');
readln(first);
writeln('Type the step');
readln(step);
writeln('Write the last value');
readln(last);
if (last<first) or ((step=0) and (last>first)) then
begin
last:=first;
first:=last;
Mnogo(fil,first,step,last,F,M,st1,s t2);
end
else
begin
writeln('Type path to your file please');
readln(path);
assign(fil,path);
{$I-}
rewrite(fil);
{$I+}
if IOResult<>0 then
writeln('Error opening file')
else
Mnogo(fil,first,step,last,F,M,st1,s t2);
readln;
end;
End.