sec(- 11pi/2) = undefined????????????????????????

according to this calculator it is 1.0472619086233173  WHY IS IT NOT UNDEFINED? 

sec(-11pi/2)

\(sec(\frac{-11\pi}{2})\\ =sec(\frac{-12\pi}{2}+\frac{\pi}{2})\\ =sec(\frac{\pi}{2})\\ =\frac{1}{cos(90^\circ)}\\ =\frac{1}{0}\\ =undefined\)

sec(-11pi/2)

I'll do it on the web2 calc and see what happens.....

sec(-11pi/2) = 1.047261908623317

Yes the is the web2 answer but it is NOT correct.  

https://www.wolframalpha.com/input/?i=sec(-11pi%2F2)

I'll message the owner of the site and see it he can fix or explain it.

You have the calculator set in degree mode if you get the 1.047... result.

Set in radian mode it gives the following:

.

Thanks Alan,

This is the first time I have seen your answer :))

Now there is one less mystery in the universe.  LOL