I used a slide rule.
What you’ve got one of the huge slide rules NASA used for the moonshot? I didn’t know they could do calculations to 19 significant digits. Wow!
(Which is an oblique way of saying I don’t believe your claim to have used a slide rule.)
If you used a slide rule and got 11.9 995 275 003 984 9 you have a slide rule about 1012 feet long. [You gain 3 digits of precision for every three orders of magnitude increase in the length. An ordinary slide rule is a foot long, and is accurate to about 3 places. I am spotting you the final "9" just to be kind.]
That means that if you moved the slide at 99.9% of the speed of light [a highly dubious proposition, but certainly not out-of-line with the other accomplishments you've claimed on this thread, like cutting cloth to nine significant figures...] it takes about 1000 seconds to move the rule, and 1000 seconds from the slider position on the rule to come back to you to read off the answer. So each multiplication, division, and square root takes about 2000 seconds. I will again spot you a couple of operations and not count the additions and subtractions, so I count at least 6 operations. That's -- generously -- 12000 seconds to run the whole thing through a slide rule.
That's three hours and 20 minutes of planet-busting labor. I'm just going to say that I'm skeptical...