# Reverse-engineering the Intel 8087's tangent algorithm: more than CORDIC (righto.com)

* **Author:** [pwg](/user?id=pwg)
* **Score:** 34 points
* **Posted:** 9 hours ago (`49858676`)
* **URL:** https://www.righto.com/2026/09/8087-tangent-cordic.html

### Comments (6)

- **kens** (9 hours ago | score: 1 | ID: `49858825`):
  > Author here for your 8087 questions...

- **jaygreco** (5 hours ago | score: 1 | ID: `49861002`):
  > Love these deep dives. It’s fascinating to see how real, low-level engineering we all take for granted today unfolded. It’s incredible that the rough equivalent of an entire 160lb digital computer was built and baked into silicon.
  > 
  > Also incredible reverse engineering. In a time when seemingly all appreciation for expertise is gone it’s so refreshing to see.

- **drob518** (1 hour ago | score: 1 | ID: `49862383`):
  > The combination of numerical methods and low-level hardware is fascinating. Those 20th century engineers were both smart and creative.

- **cmovq** (1 hour ago | score: 1 | ID: `49862492`):
  > Always thought it was strange that fptan also pushes 1 to the register stack. It now makes sense it’s to retain comparability with the 8087 which returned x and y separately and required the extra division

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