# Need a definite answer for approximately equal

August 28, 2008 11:14 AM Subscribe

Here's the deal: I've exhausted my neurons looking for some kind of answer to a mathematical symbol stumper. I'd love to know who invented, originated, or was the first individual to use the double-tilde (≈) as a means of expressing/denoting "approximately equal" in mathematics. I know that Robert-Recorde is supposed to have introduced the "equals" sign (=) in 1557. Any and all assistance is greatly appreciated. I await enlightenment.

Best answer: The use of the single tilde for geometrical similarity and the tilde & horizontal line for congruence is due to Leibniz (See also here).

But for a more definitive answer, A History of Mathematical Notations by Florian Cajori says that Greenhill first used the parallel wavy lines in 1892 (Google Books link; hopefully it works for others). You can see the Greenhill work via Google Books. The citations given in Cajori are correct, though Greenhill does not explain his notation that I can see, so he may not have actually been the first.

posted by jedicus at 12:13 PM on August 28, 2008 [1 favorite]

But for a more definitive answer, A History of Mathematical Notations by Florian Cajori says that Greenhill first used the parallel wavy lines in 1892 (Google Books link; hopefully it works for others). You can see the Greenhill work via Google Books. The citations given in Cajori are correct, though Greenhill does not explain his notation that I can see, so he may not have actually been the first.

posted by jedicus at 12:13 PM on August 28, 2008 [1 favorite]

I haven't found approximation yet in this list but its long and covers

There are some references to the first uses of the word approximation, so that may lead you down the correct path.

posted by wavering at 1:16 PM on August 28, 2008

**a lot**.There are some references to the first uses of the word approximation, so that may lead you down the correct path.

posted by wavering at 1:16 PM on August 28, 2008

*Greenhill first used the parallel wavy lines in 1892*

Except that those are not wavy lines, they're jagged; check out page 303 (near the bottom). Interesting question!

posted by languagehat at 1:48 PM on August 28, 2008

oops; Beaten to it!

posted by wittgenstein at 9:12 AM on August 29, 2008

posted by wittgenstein at 9:12 AM on August 29, 2008

This thread is closed to new comments.

posted by wittgenstein at 12:05 PM on August 28, 2008