<p>已知区域<img src="https://learnfile.20230611.cn/learnAppQuestion/b1/f8/b1f81f2d5672b9660a798fbda7e3782b.jpg" style="width: 100%;height: auto;">计算<img src="https://learnfile.20230611.cn/learnAppQuestion/67/61/67618ab83cd7bd9d71ddf3e7749e4444.jpg" style