program nurg;
uses crt;
var x1,x2,y1,y2,c,s,n,g:real;
begin
clrscr;
write('vektorid a:  ');
readln(x1,y1);
write('ja  b: ');
readln(x2,y2);
s:=x1*x2+y1*y2;
writeln('vektorite skalaarkorrutis :  ',s:5:3);
c:=(x1*x2+y1*y2)/((sqrt(sqr(x1)+sqr(y1)))*(sqrt(sqr(x2)*sqr(y2))));
writeln('cos = ',c:5:3);
if c=0 then
writeln('vektorid on perpen-sed.')
else
begin
n:=arctan(sqrt(1-sqr(c))/c);
g:=n*180/(3.14);
writeln('vektorite vaheline nurg on ',g:5:3);
end;
readln;
end.