The triangle ABC is a right angled triangle , right angled at C because it is the angle subtended by the diameter
Now OA = OB = OC = 4 cm (radii)
AB = OA + OB = 8 cm
By pythagoras theorem ,
AC =4
shade region area = area of semicircle - area of triangle
= - 1/2 × base × height
=1/2 × 16 - 1/2 × 4 ×
=8 - 8
=8()