Subject: Math problem!

Get it to integrate 1/X? :P

shiit, log in wolframalpha is ln.. I was expecting it to be log on a base 10...


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nah, I wanted to see it visually:P

log (x) is the natural logarithm in there for some reason.

to get usual log you must use log10(x)

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realised it was too easy eh:P
(edited)

no, just got the solution :)

check back of math book. answers usually there :)

could anybody show me how to solve this one:

find

lim [(x**4 + y**4)/(x**2 + y**2) + 3]
x,y->0


shouldn´t be too dificult, result is 3, but I just can´t get rid of the 0/0...

Just use l' hopital's rule:
l' hopital's rule

lim [(x**4 + y**4)/(x**2 + y**2) + 3] = lim [((x**2 + y**2)**2 - 2x**2*y**2)/(x**2 + y**2) + 3] = 0 + 3 - 2* lim [x**2*y**2/(x**2 + y**2)] = 3 - 2* lim[1/(1/y**2 + 1/x**2)] = 3

(edited)

tnx

@Pieterd, tnx also, though finding x,y fullderivative is a bit more difficult than the greuceanu´s way.
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you're welcome. transforming from carthesian to polar variables is another pretty easy way;)

oh shit yeah.. I was supposed to use polar variables, because we just studied that :D.. pitty I didn´t thought about that.

f(x)=(1+x^2)^(-2) * (2x)

find f '(x)

f '(x)= (1+x2)^(-3) * (6x^2-2)

is that the correct answer? Its written in my book, but I didn´t get that result.

I get a different sign

f'(x) = (1+x^2)^(-3) * (-6x^2+2)