# Best way to denote some trigonometric functions (“tg” vs “tan”, “ctg” vs “cot”)

What is the best way to denote tangent and other trigonometric functions: tg or tan, ctg or cot. What notation is commonly used and standardized?

• FWIW: I'd not say $\tan$ and $\cot$ are "best", but they are the notation that more people understand than $\mathrm{tg}$ and $\mathrm{ctg}$. So, if you're writing for a wide audience, you might consider using the more popular ones. – J. M. is a poor mathematician Aug 7 '12 at 11:57

In current US textbooks, $\tan$ and $\cot$ are commonly used and standardized. Also: $\sin, \cos, \sec, \csc$. In other countries, and in the 19th century, you will find others.

Some people are familiar with tg and some people are familiar with tan.So, for wide use just define the notation.It solve your's problem I think.

Standard

ISO 80000-2 Quantities and units — Part 2: Mathematical signs and symbols to be used in the natural sciences and technology

is perfectly clear: the right symbols are $$\tan x$$ (item 2-13.4) and $$\cot x$$ (item 2-13.5).

To cite the standard: "$$\text{tg } x$$, $$\text{ctg } x$$ should not be used."

• +1. Do you have a source for the ISO passages? The only thing I can find on ISO.org is an unhelpful preview and a link to purchase the document; perhaps I didn't look hard enough. The Wikipedia "ISO 80000-2" entry only makes passing reference to "sin" and "tanh" (and "arcsin" and "artanh"). (Interestingly, the entry reports that "$\sin^{-1}$" and "$\tanh^{-1}$" aren't included in the standard. I'm not sure what to think about that.) – Blue Feb 1 at 21:12
• @Blue I have access to these standards. They are rather expensive, so their publisher is doing everything it can to disable free access. If you have a specific question I can look into standard for you. – Pygmalion Feb 1 at 21:31