[Fatal]

I've tried looking through my textbook, but am unable to find any examples even remotely close to the equation, so I need some help on how to go through the problem to get the answer.

Find the derivative.

y = csc^4(3x-pi)

The answer according to the answer sheet is supposedly -10csc^5 (2x-pi)cot (2x-pi) but I am not sure if that is correct. The answer I came up with is -12csc^3 (3x - pi)cot(3x-pi) Any help would be appreciated, thanks.

 

[pat1006]

should be:
-12csc^4(3x - pi)cot(3x-pi)
you forgot that the derivative of dy/dxcsc(u) = -csc(u)cot(u) you just did dy/dxcsc(u) = -cot(u) by the looks of it.

 

[goldenratiophi]

I say the answer is -12 csc^4 (3x-pi) cot(3x - pi):

4 csc^3 (3x - pi) * -cot(3x - pi) csc (3x - pi) * (3) = -12 csc^4 (3x-pi) cot(3x - pi)

but I would agree that their answer is wrong.

PS: Welcome to Head-Fi!

 

[appophylite]

My math agrees with goldenratiophi on this one.
It's a combination of the following derivative and identity:
d/dx csc(x) = -csc(x)*cot(x)
d/dx f(g(x)) = d/dx f(g)*d/dx g(x)

 

[Fatal]

Thanks for the help. I knew something was wrong when I saw the 2x - pi in the answer. Time to get back to studying.

 

[Aimless1]

I knew there was a reason why I dropped out of engineering after calc

 

[-=Germania=-]

seriuosly.....

buy a ti-89ti .....saved me so much in high school and college engineering....

 

[runnin17]

Ha, it has been way too long since I did Calc. Oh well, all my calc knowledge had to get shoved to the side to make room for all my medical books. HEHE

 

[buddha911]

Quote:

Originally Posted by -=Germania=- /img/forum/go_quote.gif seriuosly..... buy a ti-89ti .....saved me so much in high school and college engineering....

Thats some good advice there.

 

[Kirosia]

Quote:

Originally Posted by buddha911 /img/forum/go_quote.gif Thats some good advice there.

I'm sure some teachers don't allow them during exams, so it's smarter to actually know how to do it.

 

[sebastian589]

If you are confident with your results don't worry too much about answer sheets or solutions provided in the back of the book, often times the answer provided in the back are actually wrong. I once spent a long time on a couple of Calc and Chemistry problems trying to pinpoint my mistake only to find later that the answers in the back of the book were mixed up and totally incorrect. Sometimes it pays to be a quitter

 

[Mher6]

Quote:

Originally Posted by Kirosia /img/forum/go_quote.gif I'm sure some teachers don't allow them during exams, so it's smarter to actually know how to do it.

Well of course. But in the OP's case, he could have compared the calculator result to the book result and found out that the book is indeed wrong. By the way, the TI-89 is allowed on some portions of the Calc AB/BC AP/collegeboard tests.

 

[Jon118]

My teachers don't allow calculators during exams, but the work is usually pretty simple compared to homework, where I do use a calculator, actually I usually use a program called Maple. It's a good program but apparently kind of costly. I use it from the school's servers though.

 

[ingwe]

Quote:

Originally Posted by goldenratiophi /img/forum/go_quote.gif I say the answer is -12 csc^4 (3x-pi) cot(3x - pi): 4 csc^3 (3x - pi) * -cot(3x - pi) csc (3x - pi) * (3) = -12 csc^4 (3x-pi) cot(3x - pi) but I would agree that their answer is wrong. PS: Welcome to Head-Fi!

Hmmm... I get 5. Must have forgotten to carry the 1...

 

[-=Germania=-]

You need to know your stuff for the exams, my teacher's didn't allow them in high school calc.

It does make the AP Calc exam so much faster and easier to complete. It helps you solve the small/easy parts very quickly and focus more on the difficult material.

In college, they are amazing for when you have long problem sets with the copy->paste feature and 3D graphs, along with the ability to deal with symbols.

TI-89titanium was one of the best things I ever got - I got it for Christmas my senior year of high school.....my parents wanted to say for the rest of my life that they got me a calculator for Christmas. My old one broke!