並前往https://www.sudoedu.com/zh/%E5%A4%9A%E5%85%83%E5%BE%AE%E7%A7%AF%E5%88%86%EF%BC%88multivariable-calculus%EF%BC%89%E8%A7%86%E9%A2%91%E8%AF%BE%E7%A8%8B/%E9%87%8D%E7%A7%AF%E5%88%86%E5%8F%8A%E5%85%B6%E5%BA%94%E7%94%A8%EF%BC%88multi-integrals-and-their-applications%EF%BC%89/%E6%9E%81%E5%9D%90%E6%A0%87%E4%B8%8B%E4%BA%8C%E9%87%8D%E7%A7%AF%E5%88%86%E7%9A%84%E8%AE%A1%E7%AE%97-double-integrals-in-polar-coodinates/
