# What is this symbol?

1. Nov 6, 2013

### woundedtiger4

X downward arrow a (is it limit from left)
X upward arrow a (is it limit from right)
?

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2. Nov 6, 2013

### fzero

It's the other way around. Up arrow means increasing value of $x$, so limit from the left. It's not a common notation, but it is mentioned on wikipedia: http://en.wikipedia.org/wiki/One-sided_limit

3. Nov 6, 2013

Thanks