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How to find d (area) in mathematical double integral?
The back d indicates that the integral area is a circle.

The radius of a circle is 2.

So the range is -2.

However, because the integral area is a circular area, this topic is best calculated in polar coordinates.

x = r * cos a

y = r * sin a

0 & lt= r & lt=2

0 & lt= a & lt=2π