![geometry - Why is '$\frac{r^2\pi}{d^2}=\frac{\pi}{4}$'? (a.k.a. the ratio between a square and a circle, $a=d$) - Mathematics Stack Exchange geometry - Why is '$\frac{r^2\pi}{d^2}=\frac{\pi}{4}$'? (a.k.a. the ratio between a square and a circle, $a=d$) - Mathematics Stack Exchange](https://i.stack.imgur.com/RCf7Q.png)
geometry - Why is '$\frac{r^2\pi}{d^2}=\frac{\pi}{4}$'? (a.k.a. the ratio between a square and a circle, $a=d$) - Mathematics Stack Exchange
Dave Richeson on X: "Euler proved that π/4=arctan(1/2)+arctan(1/3), which can be used for computing digits of π (using the arctangent series). I wondered if I could prove it without using a trig
![SOLVED: CALCULATION OF THE VOLUME: 1. Block V=l w h 2. Cube V=e^3 3. Cylinder V=(π)/(4) D^2 h 4. Sphere V=(π)/(6) D^3 SOLVED: CALCULATION OF THE VOLUME: 1. Block V=l w h 2. Cube V=e^3 3. Cylinder V=(π)/(4) D^2 h 4. Sphere V=(π)/(6) D^3](https://cdn.numerade.com/ask_images/d63ef184-f895-409d-a0ce-b070e8e8e089.jpg)