Draw the largest circle in a square with an area of 64 square centimeters. How many square centimeters is the area of this circle? (it's better to have a formula)

Draw the largest circle in a square with an area of 64 square centimeters. How many square centimeters is the area of this circle? (it's better to have a formula)

64=8×8
The radius of the largest circle is 8 △ 2 = 4 cm
The area of this circle is 3.14 × 4 × 4 = 50.24 square centimeter