The newest test version of HandmadeMath has been put into preview, you can get it here. This version is still in testing, so if you have any requests or issues, send them to any of the contributors, or feel free to make a pull request.
This release has added in a few new features, including several trigonometric functions, quaternions, and spherical linear interpolation, also known as SLERP.
Special thanks to all of the contributors: Miblo, Valmar33, bvisness, kiljacken, kevinmoran, and peliex.