AB = 4, cos45 = radical sign

2/2,

∴AC=BC=2 Times

Root number 2,

Similarly, OA=2,

∴AD=OD=

Root number 2,

∴ area of the shaded part = large triangle area-square area-two sector areas =2 times.

Root number 2×2 times

Root number 2÷2-

Root number 2× root number 2-

45π×2/360-

45π×2/360=2-

π/2.