# mathtask :>

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4 Sep 2008, 13:45
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Journals

ye we did that today at school

tbh its pretty easy if you know some rules :P

f(x) = sin(x) / x³

tell me f'(x) and f''(x)

have fun ::D:DD.D

if u need a hint just tell me..

btw

f'(x) != cos(x) / 3x² ..

kk prolly ive made a typo or something...but i hope most of u know what i wanted to calculate lol

i hope i could refresh some of ur brains xD

have a nice day :P

tbh its pretty easy if you know some rules :P

f(x) = sin(x) / x³

tell me f'(x) and f''(x)

have fun ::D:DD.D

if u need a hint just tell me..

btw

f'(x) != cos(x) / 3x² ..

kk prolly ive made a typo or something...but i hope most of u know what i wanted to calculate lol

i hope i could refresh some of ur brains xD

have a nice day :P

we are learning some "Differenzialregeln" for tehe upcomming staff...

this is pretty easy.....but i want to see if u can solve it ;)

anyway mathe sucks!!! mathe gk ftw

? :D

D f/g = (g * Df - f * Dg) / g²

sin(x) / x³ = -3 * sin(x)

D sin (x) = cos (x) yes

D x³ = 3x² yes

but D sin (x) / x³ = (x³ * cox (x) - sin (x) * 3x²) / x^6

AFAIK o:O

>:D

finnished math \:D/

f'(x) = (cosx) * (x³) - (sinx) * (3x²) / (x³)²too lazy to continue :S

f'(x)=-cos(x)

im not sure :/

boy i need to repeat stuff before school starts next week :[

f'(x) cos (x) = -sin (x)

f'(x)=cos(x)

f''(x)=-sin(x)

f'''(x)=-cos(x)

f''''(x)=sin(x)

:P

e^x² + 8 / x³ + 1

pff, i thought you wanted some razzle dazzle solution instead of brutally using the formula

then all my books are bullshit and all the rules

look at the solution again -.-

:) thanks for refreshing my memory about all of this stuff 8)

but u can use it only if u devide

not if u multiplicate

then it has to be u'*v+u*v'

That is, for the first derivative, I didn't check the second. Which looks really wrong on first sight, you can't randomly divide away x's :l But I don't know if I'm mistaken or not in this case, it might just be right, my memory may have failed me

That is wrong anyway, unless by x -sin(x) he means -xsin(x).

oh god razzah oh god, cant believe yo uare 17 :(

im tring to do

Prove, that for optional integers Inequality is granted my stiupid math teacher wants me to do 6 of 12 tasks of polish matholimpic :( coz i wasnt on last 3 lessons :(

heeelp!