Gudermannian Calculator
Free online gudermannian calculator. Enter your values and get instant results with the formula, step-by-step working, a worked example and FAQs — everything runs locally in your browser on Calcton, no signup required.
Gudermannian 函数 gd(x) 由 Christof Gudermann（Clein 的老师之一）在 1830 年代研究，是双曲几何与三角几何之间「不借助复数」的桥梁：它把双曲角的度量转成弧度角，自身导数恰好是 sech x——这就是墨卡托投影的纬度函数：把纬度 φ 映到等距圆柱坐标需要 x = gd⁻¹(φ)，即 artanh(sin φ)。
正演用 2 arctan(e^x) − π/2，反演用 artanh(sin y)，闭环 gd⁻¹(gd(x)) 恒等式当场验证；第二条等价形式 arctan(sinh x) 作交叉核对（x = π/2 处两式一致到 1e-14）。
参考值
gd(0) = 0，gd(1) = 0.8657694832396586（约 49.6°），gd(2) = 1.3017603360460153（约 74.6°）
gd(∞) = π/2：双曲线在无穷远处对应 90 度纬度
gd′(x) = sech x = 1/cosh x，是墨卡托投影「纬线间距」的直接来源
How to use the Gudermannian Calculator
- Fill in the inputs with your own numbers — every field shows what it expects.
- The result updates instantly as you type; no "Calculate" click needed.
- Read the result card for the main figure, the step-by-step formula, and practical notes.
Frequently asked questions
Is the Gudermannian Calculator free?
Yes — all math calculators on Calcton are free, with no sign-up required. Your inputs are processed in your browser and never sent to a server.
Is there a Chinese version of this tool?
Yes. Use the Chinese version link above — it is the same calculator with the interface in Simplified Chinese.
References
Formulas and benchmarks used by this calculator follow these published sources.
KevinContent LeadCalcton Editorial Team · Last updated 2026-09-28
Kevin maintains Calcton's formula verification and content: every calculator cites the standard it implements, worked examples are recomputed programmatically, and health benchmarks follow WHO and international guidelines.
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