From "Surely You're Joking, Mr. Feynman!": "While I was doing all this trigonometry, I didn't like the symbols for sine, cosine, tangent, and so on. To me, "si

From "Surely You're Joking, Mr. Feynman!": "While I was doing all this trigonometry, I didn't like the symbols for sine, cosine, tangent, and so on. To me, "sin f" looked like s times i times n times f! So I invented another symbol, like a square root sign, that was a sigma with a long arm sticking out of it, and I put the f underneath. For the tangent it was a tau with the top of the tau extended, and for the cosine I made a kind of gamma, but it looked a little bit like the square root sign. Now the inverse sine was the same sigma, but left -to-right reflected so that it started with the horizontal line with the value underneath, and then the sigma. That was the inverse sine, NOT sink f--that was crazy! They had that in books! To me, sin_i meant i/sine, the reciprocal. So my symbols were better." And some example here: https://tex.stackexchange.com/questions/274463/feynman-trig-notation-creating-custom-characters https://tex.stackexchange.com/questions/274463/feynman-trig-....