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Comment by twic | Hacker News Reader

Not all the screens: in my office, everyone has multiple monitors, and about half of them are in portrait orientation. They aren't special portrait monitors, they're normal monitors rotated tau/4 radians. So their plane of polarisation is perpendicular to that of the landscape monitors.

I know this because i put on a pair of sunglasses while sat at my desk, and wondered why i could still see my email, but not my IDE.

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Today I learned that tau/4 radians is a much smarter sounding way of writing 90*. Of course it takes up more space, and isn’t any more precise, so I’ll probably never remember or choose to use it. At least I won’t have to google it again the next time someone smarter than me writes it!

"90*" is unrecognizable. "90 degrees" is recognizable, but takes up more space than "tau/4". "𝜏/4" takes only 3 characters of course, same as "90°".

> "90 degrees" is recognizable, but takes up more space than "tau/4"

You forgot the unit on one of them, it's "tau/4 radians" and not "tau/4", which make it longer than "90 degrees".

"𝜏/4 rad" is still longer than "90°" too.

EDIT: I just found out that there is also a shorter symbol for rad which is the superscript c, but I don't know how to write it here and it's still longer. Wikipedia also say that it's rarely used because it's too similar to the degree sign.

how about a new single character constant that encodes tau/4 radians?

How about Ϟʹ – the ancient greek symbol for 90 :)

Who reads Ancient Greek, and why use two characters? Just use ∟ or ⦜ (Unicode “Right Angle” (U+221F), respectively “Right Angle Variant With Square” (U+299C). Don’t confuse either with ⌞, “Bottom Left Corner” (U+231E))

Tau is a Greek character, which is why I jokingly suggested this. Also, the above _is_ a single character, however, your suggestion is much more practical. The one with the square makes more sense since it may be ambiguous otherwise (90 or 270 degrees)

long after edit: I guess it's not technically one character!

Radians is a natural unit. You don’t need to specify it if you’re talking about rotations.

It is like how you need to specify % if talking percent but don’t need any units if talking perunum.

That's exactly why we come to HN, right?

If you want to save space, there is no need to mention the amount of rotation. This is sufficient:

> They aren't special portrait monitors, they're normal monitors rotated.

The amount of rotation is implied by "normal" and "portrait".

I had that happen with my polarized sunglasses at a restaurant that had their menus displayed on big vertically-rotated screens behind the counters. I kept looking around for paper menus and didn't realize there was even anything displaying on the screens until I took my glasses off.

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