Dig out a square with side length a from the circle with radius r, and calculate the area and perimeter of the remaining part

Dig out a square with side length a from the circle with radius r, and calculate the area and perimeter of the remaining part

s=πr^2-a^2
c=4a+2πr

Judgment: 1. The area of a square is in direct proportion to its side length. 2. The side length of a square is in direct proportion to its perimeter

1. Square area: side length = side length, the ratio is not a fixed value, not a positive proportion, so wrong
2. Perimeter: side length = 4, the ratio is a non-zero fixed value, so it is in positive proportion, correct
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