This one’s about p and P and mostly about pi.
First, let’s pi it up:
M-x calc P (this gives you pi) Result: 1: 3.14159265359
Well, I guess that’s a reasonable pi. But, c’mon, this is calc. Can’t we get a bit more digits? How about 100?
p 100 (sets precisions to 100) P (need to ask calc again for pi, it doesn't recalculate) Result: 1: 3.141592653589793238462643383279502884197169399375105820974944592307816406286208998628034825342117068
Well, but actually evaluating it robs it of its never-ending charm. Let’s just use it as a variable. How about calculating the area of a circle with a 5 km radius?
'5000 m 2 ^ 'pi (enter pi as a variable) * We get: 1: 25000000 m^2 pi
Yeah, sure that’s what I said I wanted, but I’ve changed my mind - now I want a number.
= 1: 78539816.3397448309615660845819875721049292349843776455243736148076954101571552249657008706335529267 m^2
Whoops, looked like I forgot to set the precision back to normal. And I can’t read this. Let’s make it a bit nicer.
Control-_ (normal emacs undo) p 7 d g (turn digit grouping on) = Result: 1: 7.853983e7 m^2
Oh, that’s because I didn’t have enough precision to render it without resorting to scientific notation. Let’s just bump the precision up again.
Control-_ (undo, since we have to redo the pi conversion with more precision) p 10 = Result: 1: 78,539,816.35 m^2
Ah, that’s better.