The winter has been crappy so far. Not much snow in my part of Winterland, and the borders are closed. No skiing.
The last couple of days I have been in the office to do some fun stuff, while everybody are gone, and the bosses don't send me mails. Today I finally found the time to do some math that I needed to work my way through. Just some straight forward differentiations. But I need to be focused, to get all the signs right.
(That's the summary of what I have produced today in the picture)