Which identity(ies) is proven right?

Question

luigi0210 · Answer

http://prntscr.com/32yha4

anonymous · Answer

o'boi

anonymous · Answer

O.O not worth it bro. Not worth it

luigi0210 · Answer

Come on guys xD

anonymous · Answer

1. seems wrong
2. ew
3. I think is right
4. #rip

anonymous · Answer

wolfram alpha to the rescue :DD

shadowlegendx · Answer

Scarry Questions D:

ganeshie8 · Answer

last one is an identity

anonymous · Answer

E

anonymous · Answer

1. wrong
3. right
2. right
4. wrong

I think o_O

anonymous · Answer

whoever wrote this question must really love torturing students. My heart goes out for them :'( and you too @Luigi0210

anonymous · Answer

Just google hyperbolic identities and compare it with the questions to see if it makes sense :d

luigi0210 · Answer

This is just calc 1 too xD

anonymous · Answer

Not really, it's second semester calc :d

anonymous · Answer

Risk it for the biscuit, and give us the right answers :3

luigi0210 · Answer

Welp, this is where 10 years of lucky guessing comes into play, I'll see the answer key after I finish the assignment >.< 
Thanks guys :3

anonymous · Answer

Sorry for being lazy :c

kinggeorge · Answer

The first is definitely wrong, as$$\cosh(x)=1/2(e^x+e^{-x})\neq1/2(e^x+e^{-x})^2$$

kinggeorge · Answer

The third is definitely right, and the fourth is definitely wrong, as the cosh(x+x) is suddenly squared for no reason.

luigi0210 · Answer

The last one is right too? Gane mentioned it was an identity.

luigi0210 · Answer

The prove seems to flow

kinggeorge · Answer

I can't see anything wrong with the second one...

kinggeorge · Answer

And the last one seems correct to me as well.

luigi0210 · Answer

Still says it's wrong >_<

kinggeorge · Answer

Ah. They lost a minus sign in the last one. So the fifth is not correct.

luigi0210 · Answer

Darn, I ran out of attempts.. now I really have to wait to see the right answer. Oh well, thanks anyways for your time sir :)

kinggeorge · Answer

These "mistakes" are just evil. Especially in the last one, as they get the correct answer, but the signs are ever so slightly off in the middles.

luigi0210 · Answer

Yea I noticed it, I just wonder why it's so hard if we're not really going to see on the test nor later on in the course. ._.

luigi0210 · Answer

*see it on

kinggeorge · Answer

To be completely fair, finding errors in proofs is important if you ever plan to do anything regarding math research. Since research is stuff that no one's done before, it's liable to have errors, and even the tiniest errors can snowball into huge catastrophes.