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Mathematics 15 Online
OpenStudy (anonymous):

how do i put this into wolfram? I can't solve them:(

OpenStudy (anonymous):

OpenStudy (perl):

you can type derivative <expression>

jimthompson5910 (jim_thompson5910):

type derivative ( 8^(4t) )/( t ) take note of the parenthesis

jimthompson5910 (jim_thompson5910):

also be careful to notice that wolfram uses "log" as a natural log

OpenStudy (perl):

wolfram uses log correctly :)

jimthompson5910 (jim_thompson5910):

I'm used to log being base 10 by default and using "ln" for natural logs

jimthompson5910 (jim_thompson5910):

so that caught me off guard at first

OpenStudy (perl):

right , in advanced maths log is ln

OpenStudy (anonymous):

OpenStudy (anonymous):

it gave me this and its wrong:"( i have 2 more chances though

jimthompson5910 (jim_thompson5910):

perhaps it wants "ln" instead of "log" also see what happens when you distribute

jimthompson5910 (jim_thompson5910):

Not sure. Sometimes computers can be really picky and wrong.

OpenStudy (perl):

did you try logarithm differentiation

OpenStudy (anonymous):

oh no :0 :"(

OpenStudy (anonymous):

i tried it in my previous example and it was wrong... i have two of these problems and i get a 100% :( So i really want to do them:"(

jimthompson5910 (jim_thompson5910):

well you can simplify that to get \[\Large f'(t) = \frac{4096^t(12t\ln(2) - 1)}{t^2}\]

jimthompson5910 (jim_thompson5910):

but that's not much of a simplification I guess

OpenStudy (anonymous):

should i try that answer? after i try it it will give me a different example

jimthompson5910 (jim_thompson5910):

sure lets see if that works

jimthompson5910 (jim_thompson5910):

not sure what form they want it in

OpenStudy (anonymous):

Yes, that was correct!!! :D

OpenStudy (anonymous):

Can you help me with one more?

jimthompson5910 (jim_thompson5910):

sure

OpenStudy (anonymous):

jimthompson5910 (jim_thompson5910):

so you'll need to type in t^(3/2)*log( sqrt(t+5) )/log(2)

OpenStudy (anonymous):

into wolfram?

jimthompson5910 (jim_thompson5910):

correct

OpenStudy (anonymous):

OpenStudy (anonymous):

like this?:) thats my answer?

OpenStudy (anonymous):

sorry I ask, i don't use it a lot and i don't wan't to learn to use it a lot, i like to learn math actually lol

jimthompson5910 (jim_thompson5910):

and that simplifies to \[f ' (t) = \frac {\sqrt {t} \left( 3\,\ln \left( t+5 \right) t+15\,\ln \left( t+5 \right) +2\,t \right) }{ 4\ln \left( 2 \right)\left( t+5 \right) }\] so yeah, definitely ugly...

OpenStudy (anonymous):

Very ugly!! lol

OpenStudy (anonymous):

Thank you :)

jimthompson5910 (jim_thompson5910):

to do this by hand, you'd use the product rule \[\large f(t) = t^{3/2}\log_{2}(\sqrt{t+5})\] \[\large f'(t) = \frac{3}{2}t^{3/2-1}\log_{2}(\sqrt{t+5})+t^{3/2}\frac{1}{\ln(2)*\sqrt{t+5}}\] \[\large f'(t) = \frac{3}{2}t^{1/2}\log_{2}(\sqrt{t+5})+t^{3/2}\frac{1}{\ln(2)*\sqrt{t+5}}*\frac{1}{2}(t+5)^{-1/2}\] then you simplify that to get what wolfram is saying

OpenStudy (anonymous):

Thank you for teaching me the steps, yes I actually tried it and got a mess and knew it was wrong right away lol

jimthompson5910 (jim_thompson5910):

well it's definitely not a clean simple thing (unfortunately)

OpenStudy (perl):

its easier to change the base first

OpenStudy (perl):

also bring the exponent 1/2 down in front log_2 (t + 5)^1/2 = 1/2 * log_2 ( t + 5) = 1/2 * ln ( t + 5) / ln 2

OpenStudy (perl):

that is a much easier expression to take the derivative of

OpenStudy (perl):

log_2 (t + 5)^1/2 = 1/ (2 * ln 2 ) * ln ( t + 5)

jimthompson5910 (jim_thompson5910):

good point, that should help simplify things

OpenStudy (anonymous):

Oh i see it, can i always change the base first? It won't change anything right?

jimthompson5910 (jim_thompson5910):

no because \[\Large \log_{b}(x) = \frac{\log(x)}{\log(b)}\] \[\Large \log_{b}(x) = \frac{\ln(x)}{\ln(b)}\]

jimthompson5910 (jim_thompson5910):

the logs on the right side can be any base

jimthompson5910 (jim_thompson5910):

so that's why nothing changes

OpenStudy (anonymous):

Oh!!!!! Okay okay :D i understand that!! Thank you, that makes so much sense

jimthompson5910 (jim_thompson5910):

np

OpenStudy (anonymous):

Good bye guys, I will now study for chemistry! Thank you :D

jimthompson5910 (jim_thompson5910):

have fun

OpenStudy (anonymous):

hold on look:(

OpenStudy (anonymous):

OpenStudy (anonymous):

it gave me this one now:"(

jimthompson5910 (jim_thompson5910):

I got the same thing. Maybe they want you to use the * to mean multiply? hmm

jimthompson5910 (jim_thompson5910):

ok now I get \[\Large f'(t) = {\frac {\sqrt {t} \left( 3t\,\ln \left( t+4 \right)+12\,\ln \left( t+4 \right) +2\,t \right) }{ 4\left( t+4 \right) \ln \left( 2 \right) }}\]

jimthompson5910 (jim_thompson5910):

basically the same as before, just with different numbers

OpenStudy (anonymous):

yea, but it always throws me off, sometimes they change one small thing and i make a huge mistake and get a whole different answer lol

OpenStudy (anonymous):

let me try it:

jimthompson5910 (jim_thompson5910):

well again you'll use the product rule and the chain rule will pop up when it comes to deriving the log or you can simplify things first to make it a bit easier, then derive next

OpenStudy (anonymous):

still wrong:(

OpenStudy (anonymous):

yes its the same concept as the first one, correct?

jimthompson5910 (jim_thompson5910):

try using * for multiplication symbols

jimthompson5910 (jim_thompson5910):

yes, just the numbers have changed

jimthompson5910 (jim_thompson5910):

oh wait, I missed a number, one sec

jimthompson5910 (jim_thompson5910):

\[\Large f'(t) = \frac {\sqrt {t} \left( 3\,\ln \left( t+4 \right) t+12\,\ln \left( t+4 \right) +2\,t \right) }{ 12\left( t+4 \right) \ln \left( 2 \right) }\] ok got that now

jimthompson5910 (jim_thompson5910):

I had the wrong log base before

OpenStudy (anonymous):

it changed it to this

OpenStudy (anonymous):

OpenStudy (anonymous):

I can just change the #'s no?

jimthompson5910 (jim_thompson5910):

third time is the charm (hopefully lol) \[\Large f'(t) = \frac {\sqrt {t} \left( 3\,\ln \left( t+3 \right) t+9\,\ln \left( t+3 \right) +2\,t \right) }{ 4\left( t+3 \right) \ln \left( 5 \right) }\] is what I get

jimthompson5910 (jim_thompson5910):

and yeah, the numbers are just changed

OpenStudy (anonymous):

okay let me try my last chance lol

OpenStudy (anonymous):

Perfect:) i got a 100% THANK YOU!

jimthompson5910 (jim_thompson5910):

glad it finally accepted it lol

OpenStudy (anonymous):

me too!!! Thanks to you!!

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