Since the radii of the three circles are equal, it can be seen that the three sides of the triangle are equal (side = radius+radius), and the triangle is a congruent triangles with each angle of 60.

Shadow area = the sum of three sector areas with a radius of 8cm and a central angle of 60.

3×(8? ×3. 14×60/360)

=200.96cm？

The perimeter of the middle part of the triangle:

The arc length of three sectors with a central angle of 60 is also equal to half the circumference of a circle with a radius of 8cm.

8× 2× 3.14÷ 2 = 25.12cm