How do you know how long the bannister is without Pythagoras?

With a ruler? 😛

Wouldn't you like to know BEFORE you order the lumber for the stairs? But there are lots of other cases (and, for knitwear, the diagonal is too stretchy for a ruler to give you the best measurement).

😮

Keep up the good work.

You might not always be able to get close enough to measure something with a ruler.

Then I could use trigonometry! Oh wait that's way harder than Pythagoras LOL