🥚 椭圆计算器Ellipse Calculator
由长半轴和短半轴计算椭圆面积、周长（AGM 精确算法）、离心率、焦距和半通径。Area, perimeter (exact AGM method), eccentricity, focal distance and semi-latus rectum of an ellipse from its semi-axes.
使用说明与常见问题How-to & FAQ
「椭圆计算器」是什么？What is the Ellipse Calculator tool?
由长半轴和短半轴计算椭圆面积、周长（AGM 精确算法）、离心率、焦距和半通径。Area, perimeter (exact AGM method), eccentricity, focal distance and semi-latus rectum of an ellipse from its semi-axes.
如何使用「椭圆计算器」？How do I use the Ellipse Calculator tool?
在「椭圆计算器」中，填写「半轴 a」、「半轴 b」等参数，结果会随输入实时计算并显示在下方。In the Ellipse Calculator: Fill in "Semi-axis a", "Semi-axis b"; results are recalculated instantly as you type.
椭圆周长怎么算、准不准？How is the perimeter computed, and how accurate is it?
椭圆周长没有初等函数的精确公式。本工具用算术–几何平均（AGM）算法计算完全椭圆积分，结果精确到双精度浮点（约 15 位有效数字），扁长椭圆同样准确。不使用近似公式。There is no closed-form formula. This tool evaluates the complete elliptic integral with the arithmetic–geometric mean (AGM), accurate to double precision (about 15 significant digits) even for very elongated ellipses. No approximation formula is used.
「椭圆计算器」免费吗？需要注册吗？Is the Ellipse Calculator free? Do I need an account?
「椭圆计算器」完全免费，无需注册或安装，打开网页即可使用，手机和电脑都能用；输入的内容只在你的浏览器本地处理。The Ellipse Calculator is completely free with no sign-up or install and works on phones and desktops; what you enter is processed only in your browser.