# Search results

1. ### I don't understand the meaning of f^(39)(pi/2)?

every fourth derivative gives you sin(x) I think you can take it from there
2. ### I don't understand the meaning of f^(39)(pi/2)?

I think they mean take the 39th derivative of sin(x) and evaluate that at pi/2 the 2nd derivative -sin(x) third is -cos(x) and fourth is sin(x)......
3. ### Why was Tesla obsessed with the number 3?

I agree. The history channel once upon a time fell in the 0.1% but now...ancient aliens and swamp people lol. The only documentaries I trust now are on science channel.
4. ### Why was Tesla obsessed with the number 3?

It's mentioned in the documentary about tesla on the history channel. The name of the documentary is "The History Channel-Modern Marvels:Nikola Tesla:Mad Electricity." Mind you they also air ancient aliens so much its as if they believe aliens were apart of everyday life in antiquity.
5. ### Laurent series and partial fractions

Homework Statement find the laurent series of sin(2z)/(z^3) in [z]>0 Homework Equations The Attempt at a Solution I am completely confused. I can understand some of the examples given on laurent series, like using partial fractions and then finding geometric series. Do I rewrite...
6. ### Complex analysis

ohhhhh nevermind i finally got it you rewrite the denominator as (z+i)(z-i) then do the partial fraction. so simple! you were right rizardonthanks
7. ### Complex analysis

So I do the partial fraction after i expand out? expanding (z+i)/(z^2+1) I get (x+yi+i)/(x^2+2xyi-y^2+1) how am I supposed to factor the denominator?
8. ### Complex analysis

all i want is a simple hint i don't want anyone to do the problem for me I just want a little help. just a little push in the right direction would be so helpful.
9. ### Complex analysis

Homework Statement write f(z)= (z+i)/(z^2+1) in the form w=u(x,y)+iv(x,y) Homework Equations The Attempt at a Solution I tried using the conjugate and also expanding out algebraically but I can not seem to get the right answer. I know what the answer is...
10. ### Keys are locked

it turns out that that individual spilt something on it. he just confessed, so a new keyboard it is....
11. ### Laplace inverse

which one??????
12. ### Laplace inverse

Homework Statement s2/((s2-1)(s-1)2) Homework Equations laplace tables The Attempt at a Solution I attempted the shifting method and also partial fraction method but efforts were fruitless
13. ### Keys are locked

Someone hit some random combination of keys that locked up some of the keyboard. A few of them started working but there is still a couple that don't work. Does anyone know how to unlock these keys?:uhh:
14. ### Simple differential equation

Thank you very much you have been very helpful. I appreciate it
15. ### Simple differential equation

oh yeah i know i put cos by accident, but that is the solution right? I arrived at this solution by a long trial and error method. any way to quickly get at it in general?
16. ### Simple differential equation

is y= -2.5xcos(x) right?
17. ### Simple differential equation

try multiplying what by a power of x?
18. ### Simple differential equation

Homework Statement y''+y=5cos(x) Homework Equations y=Acos(x)+Bsin(x) e^ix=cos(x)+isin(x) The Attempt at a Solution I tried using compbinations of these equations to try and solve but i'm lost. Any suggestions would be greatly appreciated!

anyone?
20. ### Bernoulli in disguise

Homework Statement I think this is a bernoulli equation in disguise (y^7-6x)y'+y=0 Homework Equations I'm having trouble putting it in the form of y'+P(x)y=Q(x)y^n The Attempt at a Solution I've tried to divide out (y^7-6x) as well as some other alebraic manipulation but i keep...
21. ### Gaussian electron cloud

Homework Statement draw the field lines of a simple hydrogen atom model. A case is given where a proton is surrounded by an electron cloud. Without getting into quantum mechanics how would represent the field lines of this mini sphere inside and out. Homework Equations gauss's law The...
22. ### Integrating volumes

thank you tiny tim
23. ### Integrating volumes

Homework Statement Revolve the region bounded by x=0, x=1, y=0 and y=x^5 about the y axis use shells to find the volume I know how to set up the integral I just don't know where i'm integrating from. Is it from 0 to 1?
24. ### Gauss's law help

So the net charge on the inner surface would become positive 6 micro coulombs?
25. ### Gauss's law help

Would the charge distributes be the charge density per area plus the the point charge in the center?
26. ### Gauss's law help

Homework Statement A hollow spherical conducting shell has a uniformly distributed total surface charge density of -15\muC/m^2. It's outer surface has a radius R1=0.25m. Its inner radius is R2=0.15 m. A point charge, Q= -6.0\muC, is placed at the center of the spherical charge. Determine the...
27. ### Box puzzle

Yes, being a new user here I lacked certain specifications that would indeed clarify the problem. When I said "material" I meant it to be infinitely thin, like a plane. And the material is perfectly malleable. And when I refer to "box/cube", I mean it must have all equal faces or sides. I didn't...
28. ### Box puzzle

A sheet of material 1000 cm^2 is given to you to construct a box/cube with no lid. What is the maximum volume of the cube that can be created in cm^3?
29. ### Wave equation

[b]1. Homework Statement [/b Determine whether the function D=A sin kx cos \omegat is a solution of the wave equation. Homework Equations D=Asin (kx-\omegat) The Attempt at a Solution sorry completely lost please help Homework Statement Homework Equations The...
30. ### How many hrs do you sleep?

can you give an age? don't have to be exact just range, like 20-25 or 25-30 years of age etc.