## How to label the 13th floor ** Note: Some posts on Math-Fail are user-submitted and NOT verified by the admin of the site before publication. If you find this post to be distasteful, non-math related, ?or something worse?, then definitely leave a comment letting me know. Thanks very much! Mike **     (4.27 from 22 votes) Loading...

1. sigh

Further evidence that explaining the joke ruins it. 1 0

2. r0m1

Except that the absolute value is unnecessary, the square root of 169 is 13, it can’t be -13, otherwise square root wouldn’t be a function.
So the joke is more of a fail. 14 5

• AL 4 12

• r0m1 8 1

• AL 4 8

• Chad

Using the square root symbol denotes the principal square root, which is always positive. Thus the absolute value is not needed. For example, this is why there is a ± in the quadratic formula.

And yes f(x) = sqrt(x) is a function.

http://en.wikipedia.org/wiki/Square_root 8 0

• BtaylorTheRogue 1 5

3. tudza

12′ 0 0

4. Alex

http://en.wikipedia.org/wiki/Square_root

The second and third paragraphs explain this. The square root sign denotes the positive square root. If you are referring to the negative root, you just put a minus sign in front of it. If you are referring to both roots, you use the ± sign. 🙂 6 0