Given a rational Heronian triangle of side lengths \frac pd, \frac qd,\frac rd, the scale factor \frac d{\gcd(p,q,r)} produce a rational Heronian triangle such that its side lengths a, b,c are setwise coprime numbers. It is proved below that the area is an integer, and thus the triangle is a Heronian triangle. Such a triangle is often called a primitive Heronian triangle.
