Feuerbach's circle can be drawn by connecting certain points of these figures.
Feuerbach's circle can be drawn by connecting certain points of these figures. The center of that circle, also known as the nine-point circle, lies on the Euler line in one of these shapes. One can calculate their area using the semiperimeter according to (*) Hero's Formula. Other formulas used with these shapes include the law of sines and the Pythagorean Theorem. Name these shapes whose interior angles sum to 180 degrees, and which contain three sides.
Feuerbach's circle can be drawn by connecting certain points of these figures.
{triangle}s [accept more specific answers, as long as they mention {triangle}s, until "Pythagorean"; after that, accept only right {triangle}s]