uses crt;
var a,b,c,alfa,beta,gamma:real;
function arccos(x:real):real;
begin
arccos:=arctan(sqrt(1-sqr(x))/x);
end;
begin
write('A B C -> ');
readln(a,b,c);
if (a>=b+c) or (b>=c+a) or (c>=a+b) or (a<=0) or (b<=0) or (c<=0) then write('Такого тр-ка не существует!') else
begin
alfa:=arccos((sqr(b)+sqr(c)-sqr(a))/(2*b*c));
beta:=arccos((sqr(a)+sqr(c)-sqr(b))/(2*a*c));
gamma:=arccos((sqr(b)+sqr(a)-sqr(c))/(2*a*b););
writeln('Alfa = ',alfa:0:4);
writeln('Beta = ',beta:0:4);
writeln('Gamma = ',gamma:0:4);
end;
readln;
end.