An angle inscribed in a semicircle is always a right angle. Therefore ΔABC is a right triangle, and we can take its two legs as its base and height. So the area of ΔABC = = = 80 Since ΔABR is a right triangle, we can find the hypotenuse AB using the Pythagorean theorem: ABē=ACē+CBē ABē=16ē+10ē ABē=256+100 ABē=356 AB= = = AB is the diameter of the semicircle. Since the radius is half the diameter, the radius is . Area of a whole circle is so Area of a semicircle = So the area of this semicircle is = = 139.8008731 So the area of the portion of the semicircle which is outside of the inscribed right triangle ΔABC is area of semicircle - area of triangle = 139.8008731 - 80 = 59.80087308 Edwin