program tam_giac;
var a,b,c,cosc,sinc,s:real;
begin
write('Nhap vao 3 so thuc duong a,b,c : ');readln(a,b,c);
if (a<0) or (b<0) or(c<0)then write('a,b,c khong phai la 3 canh cua tam giac')
else
if (a<b+c) and (b<c+a) and(c<a+b) then
begin
if (sqr(a)=sqr(b)+sqr(c))or(sqr(b)=sqr(a)+s...
then write('a,b,c la canh cua mot tam giac vuong ')
else if(a=b)and(b=c) then write('a,b,c la 3 canh cua mot tam giac deu')
else if (a=b)or(b=c)or(c=a) then write('a,b,c la 3 canh cua tam giac can')
else write('a,b,c la 3 canh cua mot tam giac thuong ');
cosc:=( sqr(a)+sqr(b)-sqr(c) ) /(2*a*b);
sinc:=sqrt( 1-sqr(cosc));
s:=1/2*a*b*sinc;
write('Dien tich tam giac la ',s :10:3);
end
else write('a,b,c khong phai la 3 canh cua mot tam giac');
readln
end.