Recent content by Spectre5

hm...I've found the solution. For anyone that stumbles upon this in the future... The Jacobian DOES work, even for those non-coplanar faces. My mistake was that I was integrating the Jacobian evaluated at the center of the parametric element. For a 2D element using the shape functions I use...

Hello, I'm trying to calculate the volume of a hexahedron. I know how to do this for any arbitrary hexahedron as long as the 4 points of each face are coplanar (by using shape functions to calculate the Jacobian in a parametric space or using 5 tetrahedrons). However, the catch is that two...

In practice, they can be used to calculate the basis of new coordinate system which make certain calculations easier. For example, in 3D rigid body mechanics, you can solve the eigenevalue/eigenvector problem to get the coordinate system in which all products of inertia are zero...

Yes, you can use ANY form of f(x), IF it works as a solution...try some other random forms of f, and you shall find that they do not work (their constants will be forced to be zero, thus creating the already-known, trivial solution, zero). For example, using Psuedo's example, try a solution of...

I am also an engineering student, and I love math as well (Mechanical Engineering, Mathematics Minor)...But I would tend to agree with what others have said...most of my fellow students (in ME) do not like math. I find it rather disturbing that so many of them absolutely hate math...It...

Look at your equations for the velocity and potential energy, they are incorrect. Look at the disk and rod completely separately for this problem. Assume a homogenius rod and a homogenius disk (unless otherwise specified) and then you the velocity of the center of mass for the rod and disk...

Those come from solving the ordinary differential equations of f and g separately. Do you have any experience with solving ODE's? If not, then you should really study them first...such as separation of variables, integrating factor method, etc, etc. The way you actually get cos and sin in...

Thank you for the suggestions. I will look into those. In that pde book, does it teach pde's from the complex perspective or trigonometric? i.e. My pde book now avoids as many uses of complex variables as possible and converts everything to sin/cos and sinh/cosh instead of complex...

No suggestions?

Hey, I am looking for some recommendations on books covering partial differential equations and another one on complex analysis. I don't have a lot of extra money, so I am kind of hoping that someone has experience with some of the Dover books, and could possible recommend any of them? I...

Hey, The rank of a matrix is the number of linearly independent rows in the matrix. You can find the rank by performing Gaussian elimination. The rank will then be the number of non-zero rows in the resulting matrix.

yes, that's correct

errr...um ok...I guess i'll just have to try thinking about it some more...anyways thanks for the help guys!

Isn't the unit r vector just in the outward direction from the z axis though? I realize that in x-y-z coordinates that the r vector would change with changing theta, but cylindrical coords are different EDIT: No, you just looked like a mind reader because it was a response to this post...

ok, ok...so I'm an idiot...I think I got it now, thanks for all the help! One last thing though, why do the r and theta vectors depend on theta whereas all the others don't? Obviously z would not depend on theta, and obviously theta would depend on the angle theta, but why does r depend on...