[微积分] 利用极坐标计算二重积分
https://wenku.baidu.com/view/3e62df30b90d6c85ec3ac670.htmlhtml
https://baijiahao.baidu.com/s?id=1614655524397070040&wfr=spider&for=pcide
1. 极坐标的定义
已知平面上一点P，在直角坐标系下坐标为（x,y），极坐标系下的坐标为spa
2. 推导
即将$dxdy$ 转换为：$rdrd\theta$htm
3. 计算
1) $\alpha <= \theta <= \beta$; $\varphi_1(\theta) <= \theta <= \varphi_2(\theta)$blog
2) $\alpha <= \theta <= \beta$; $0 <= r <= \varphi(\theta)$get
3) $0 <= \theta <= 2\pi$; $0 <= r <= \varphi(\theta)$io