⏢ 梯形计算器Trapezoid Calculator
输入梯形的上底、下底和高求面积和中位线；再填两条腰长可求周长和四个内角，也可以选择由面积反求高。Find a trapezoid's area and midsegment from its two bases and height; add the two legs to get the perimeter and all four angles, or work back from the area to the height.
使用说明与常见问题How-to & FAQ
「梯形计算器」是什么？What is the Trapezoid Calculator tool?
输入梯形的上底、下底和高求面积和中位线；再填两条腰长可求周长和四个内角，也可以选择由面积反求高。Find a trapezoid's area and midsegment from its two bases and height; add the two legs to get the perimeter and all four angles, or work back from the area to the height.
如何使用「梯形计算器」？How do I use the Trapezoid Calculator tool?
在「梯形计算器」中，填写「求解」、「上底 a」、「下底 b」、「高 h」、「面积」等参数，结果会随输入实时计算并显示在下方。In the Trapezoid Calculator: Fill in "Solve for", "Base a (top)", "Base b (bottom)", "Height h", "Area"; results are recalculated instantly as you type.
梯形面积公式？Trapezoid area formula?
面积 = (上底 + 下底) × 高 ÷ 2；中位线 = (上底 + 下底) ÷ 2，所以面积也等于中位线 × 高。Area = (a + b) × h ÷ 2; the midsegment is (a + b) ÷ 2, so area also equals midsegment × height.
为什么要填腰长？Why enter the legs?
只知道两底和高时，梯形形状并不唯一；填入两条腰长后才能确定周长和内角。Bases and height alone do not fix the shape; the two legs are needed to get the perimeter and angles.
计算精度如何？How precise are the results?
「梯形计算器」使用 JavaScript 双精度浮点数（约 15–16 位有效数字）；极大或极小的数值可能存在精度误差。The Trapezoid Calculator uses double-precision floating point (about 15–16 significant digits); very large or very small values may lose precision.
「梯形计算器」免费吗？需要注册吗？Is the Trapezoid Calculator free? Do I need an account?
「梯形计算器」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 Trapezoid 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.