![Column Why does π/4= arctangent 1=4 arctangent (1/5)- arctangent (1/239) hold true? | Japanese Mathematics in the Edo Period Column Why does π/4= arctangent 1=4 arctangent (1/5)- arctangent (1/239) hold true? | Japanese Mathematics in the Edo Period](https://www.ndl.go.jp/math/e/s1/images/c4_2_10.gif)
Column Why does π/4= arctangent 1=4 arctangent (1/5)- arctangent (1/239) hold true? | Japanese Mathematics in the Edo Period
![trigonometry - What is the value of $\arctan(1/2)+\arctan(1/5)+\arctan(1/8)$? - Mathematics Stack Exchange trigonometry - What is the value of $\arctan(1/2)+\arctan(1/5)+\arctan(1/8)$? - Mathematics Stack Exchange](https://i.stack.imgur.com/jKnbo.png)
trigonometry - What is the value of $\arctan(1/2)+\arctan(1/5)+\arctan(1/8)$? - Mathematics Stack Exchange
![The function f (x) = arctan(1/x) − x/(1 + x 2 ) plotted with its real... | Download Scientific Diagram The function f (x) = arctan(1/x) − x/(1 + x 2 ) plotted with its real... | Download Scientific Diagram](https://www.researchgate.net/publication/257341129/figure/fig2/AS:670006954188813@1536753514531/The-function-f-x-arctan1-x-x-1-x-2-plotted-with-its-real-entire-majorant-and.png)
The function f (x) = arctan(1/x) − x/(1 + x 2 ) plotted with its real... | Download Scientific Diagram
![I've noticed this interesting equality. Why does this hold? And how should I go about proving this? I thought about using taylor expansions, but that just seems like overkill to me, and I've noticed this interesting equality. Why does this hold? And how should I go about proving this? I thought about using taylor expansions, but that just seems like overkill to me, and](https://preview.redd.it/ive-noticed-this-interesting-equality-why-does-this-hold-v0-jimci8gdgnlb1.png?auto=webp&s=2bff0383347c1d3bb792fb2c01afbce0ac9886ce)