I remember one time when I was working in construction. A group of guys were crawling around in the rafters of a big building trying to install diagonal bracing. Every measurement was different and they were having a hard time trying get the measurements and figure out the angles. It was such a cumbersome process that they were literally putting their lives in danger.
They asked me to cut some boards for them. I pointed out that I already knew some of the dimensions of the building from the plans and if they just got one more easy measurement per location, I could figure out the measurements and angles from the ground. I often carried a scientific calculator in my tool belt. I just did some basic trigonometry and cut the boards for them. It saved a lot of time and was much more accurate.
There were a lot of other times when some simple mathematics made things easier or safer. There were times when I was called on to install curved forms for concrete. It was common to just eyeball and guestimate the forms, but if you could calculate how long the form was supposed to be, it tended to just fall into place almost perfectly.