# Recent content by r.a.c.

1. ### Very Easy Differential Question

Homework Statement We have f(x,y) = \frac{xy}{x^2+y^2} Show that the first partial derivative w.r.t. x and w.r.t y exist Homework Equations f(x+dx,y)-f(x,y) = a(dx) + o(dx) where a is some number and o(dx)(not o multiplied by dx rather a 'function', if so to say, o of dx) is such that...
2. ### Tuning Fork - Simple Harmonic Motion

I don't know why the Latex failed but anyway it is quite a complicated equation with a damping effect and the part without the damping. My question was how can you get to the ODE in the first and keep going and second how does the damping come in.
3. ### Tuning Fork - Simple Harmonic Motion

That much I know about the tuning fork. My point is the ODE of the harmonic oscillator. In fact we have the ODE m\frac{d^2x}{dt^2} + b\frac{dx}{dt} + kx = F cos(wt) Which leads eventually (with damping to) x = Ae^-^\gamma ^t cos(w_1 t + \theta) + \frac{Fsin(wt+ \theta _0)m}{[(w^2_0 - w^2)^2...
4. ### Tuning Fork - Simple Harmonic Motion

This topic has proved itself to be a hard one in, in terms of looking it up online. I'm interested in simple harmonic motion, in specific that of a tuning fork vibrating between two electromagnetic devices, a microphone ad a detector. My main interest in it is to write a lab report about an...
5. ### Solving partial differential equations

If you are up to level with engineering math course then you should be able to tackle this. In the end engineers do have to take partial differential equations. If you know all basic calculus and are comfortable with the complex plane (Not as in need to know full complex analysis, just a mild...
6. ### Epsilon-limit proof for real number sequences

The sequence an converges therefore it is bounded. So every an<M where M is some number. So the sum becomes less that (M-L) ...n-N+1 times over n and from there go on.
7. ### PDE math homework help

Thanks but I found the answer to this. I think this is done.
8. ### 2 dimensional PDE and a higher dimension problem.

Homework Statement The 2d PDE Assume f\in S(\mathbb{R}^2) (Schwartz space) Then solve u_{xx}(x,y) + 2u_{yy}(x,y) + 3u_{x}(x,y) -4u(x,y) = f(x,y) ; (x,y) \in\mathbb{R}^2 u_{xxxx}(x,y) - u_{yy}(x,y) + 2u(x,y) = f(x,y) ; (x,y) \in\mathbb{R}^2 Homework Equations The relevant...
9. ### If f is integrable over E iff |f| is integrable over E.

But I don't get it. Graphically that is. The integral on R of higher dimensions is analogue to summation of R. Now if f = sinx /x the summation (if x belongs to N) is finite but |sinx/x| is not finite. Doesn't the same apply for the integral? Let x belong to R of higher dimensions. Wouldn't the...
10. ### PDE math homework help

No I'm not missing anything in the solution. That's the problem. If the constraints on the extremities of x were there it would be a piece of cake. And if we had them then there would be no need for f to be belong to C or PS. Even in the question it tells us to solve the PDE using fourier series.
11. ### Inverting Consequences of Uniform Convergence

Thanks a lot. And will do.
12. ### PDE math homework help

Homework Statement We are given f \epsilon C(T) [set of continuous and 2pi periodic functions] and PS(T) [set of piecewise smooth and 2pi periodic functions] SOlve the BVP ut(x,t) = uxx(x,t) ; (x,t) belongs to R x (0,inf) u(x,0) = f(x) ...
13. ### Inverting Consequences of Uniform Convergence

Hi. Now you probably know that if a function fk(x) converges uniformly to f(x) then we are allowed to certain actions such as limn-> \inf \int f (of k) dx = \int f dx In other words we are allowed to exchange limit and integral. Now say we have any sequnce valued function fk(x) . And we...
14. ### Mechanics which is lagrangian

And the lagrangian (as stated by my physics professor) is physical but it has something to do with high energy physics.
15. ### Mechanics which is lagrangian

The hamiltonian is a constant if no dissipative forces are present. That's how you can build a phase space for idealistic examples, by looking at the hamiltonian. The Susskind lectures are really good. Is this the same for all stanford (or any other university for that matter) courses?