People occasionally took me for a private detective or IRS agent when I walked into certain bars in the afternoon to have a drink about 40 years ago.
I learned to bring in a yellow pad and pen and then take the general 2nd degree equation in x and y, write it in large letters at the top and then "derive" the common conic equations from it.
After a number of peeks at what I was doing, everybody relaxed and I could enjoy my drink as well.