(2) The minimum diameter of the disc needed to cover the three square cardboard in Figure ② is 102cm.
Fig. ③ The minimum diameter of the disc required to cover three square cardboard is102 cm; ;
(3) If the distance from the center of the circle to the top horizontal line is X and the distance from the bottom horizontal line is Y, then x+y= 10,
∵OB=OA,∴AK=BK,
According to Pythagorean theorem,
x2+(52)2=y2+52,
X= 19×5 16,y= 13×5 16,
Then ob = (13× 516) 2+52 ≈ 6.44,
The minimum diameter of the disc is 12.88 cm. ..
(4) From the above conclusion, we can draw a conclusion that a. A disk can cover three square cardboard.