There are always programmers who didn't not bothered to remember their math course. They usually have enough coding knowledge that they provide some value, but from a technical perspective they are a slowly-increasing liability. As an example: I work with a developer who is 10 years younger, but still doesn't understand how to extract rotation matrix from coordinate transformation matrix and cannot be trusted to code gradient descent without causing a mess that somebody else will have to clean up. On top of that, he is really resistant to the idea of refreshing his math skills; I suspect he dislikes people he considers senior to him making suggestions about how to improve his math knowledge. How do you help somebody like this to improve their skill-sets? And, most importantly, how do you do so without stepping on anybody's feelings?