derivative of 9sinh(lnt). I thought it should be (9cosh(lnt))/t but apparently that is incorrect...please help!!

Question

irishboy123 · Answer

go back to the definition of sinh -- > sinh x = 1/2 (e ^ x - e^ -x)

sub into that and see where you go with e^ ln t etc

anonymous · Answer

Thanks! Didn't think to do that

anonymous · Answer

I got 9/2(2t) before taking the derivative, and then just 9 after the derivative but that was wrong still

zarkon · Answer

your original answer is correct

anonymous · Answer

not according to the online hw website. It marked it as wrong

zarkon · Answer

your answer is correct...but it can be simplified.  Maybe then will the website understand your answer

zarkon · Answer

$$\frac{9\cosh(\ln(t))}{t}$$
$$=\frac{9}{2}\left[\frac{e^{\ln(t)}+e^{-\ln(t)}}{t}\right]$$
$$=\frac{9}{2}\left[\frac{t+\frac{1}{t}}{t}\right]$$
$$=\frac{9}{2}\left[1+\frac{1}{t^2}\right]$$

anonymous · Answer

I tried that too and it didn't work...

zarkon · Answer

http://www.wolframalpha.com/input/?i=derivative++9sinh%28ln%28t%29%29

zarkon · Answer

then your website doesn't work  ;)

anonymous · Answer

I know that is the answer and all that...I'm probably just going to talk to my teacher about it

zarkon · Answer

just know that what you did was correct.  The website is only as good as the people that programmed it.