Recent content by John777

Homework Statement y''' - 5y'' + t^4 = 0 y(o) = y'(0)=0 y''(0)=1 The derivs are respect to t. I converted everything into s and factored Y(s) = (S^5+24)/(s^7(s+5) = A/s^7 + B/s^6 + C/s^5 + D/s^4 + E/s^3 + F/s^2 + G/s + H/(s+5) Normally you would go through multiplying the...

What are the laplace transformations of y"' and y"". Any table I can find only goes up to y". Thanks.

Great! Thanks for the help I need the basics since I haven't done math in a while and am now going back to school. My professor seems to think everyone has been practicing math everyday and knows a lot, whereas I didn't going into the class. Its getting pretty late so I will probably try and...

Ok I see they are both x. I think how the forum was displaying it, I was a little confused as to what you were writing.

So plugging in x for f(x) in the first function will be result in an answer of x. I not totally sure if you are multiplying the second thing by f(x) or not but if you are it would be x^2. So by in front of the operation you mean to the right as we read so d(x^2)/dx would be 2x?

I am getting more confused. u.grad = ux d/dx + uy d/dy + uz d/dz In this example the U terms seem to be in front of the derivation operators. I believe you are referring to the dot product? in your example I believe u.grad = ux d/dx + uy d/dy + uz d/dz following the definition where as a...

so u.grad = ux d/dx + uy d/dy + uz d/dz so if u equaled 2xi + 4xyj + 5xyzk u.grad would equal 2 + 4x + 5xy? and if it were (u.grad)V where V = Vx + Vy + Vk it would equal 2Vx + 4xVy + 5xyVk?

How come it is ok to leave the U outside the partial? I apologize for my ignorance but I am new to this stuff.

I'm not quite sure how you would do that derivation, could you just give me a quick sample?

Here is just the i components worked out: left side: d/dx * (UxVx +UyVy + UzVz)i right side: each line will represent one part of right side of given problem (VxUx * d/dx + VxVy * d/dy + VxUz * d/dz)i (VxUx *d/dx + VyUx * d/dy + VzUx * d/dz)i (VxUy * d/dx - VxUy * d/dy +...

Ha! your correct it was a typo my mistake. here is the correct problem: grad(U.V) = (U.grad)V + (V.grad)U + Ux(gradxV) + Vx(gradxU)

I see your rationale but in trying to make the left side equal the right side how do I cancel out terms such as VzUy d/dx that do not appear on the left side? (This term I am referring to results from the third Ux(gradxV) term. For example the entire left side i component has three terms, but...

I am trying to prove two things equal that involves a bunch of dot products, cross products and curls. I can't remember the exact problem, but this demonstrates my question.My question is the left side \delta/\deltax*(UxVx + UyVy + UzVz) The right side is \delta/\deltax*(VxUx + VyUy + VzUz +...

Could someone please clarify a simple order of operations related to cross product? A x (B x C) = ? I am not sure between the these two options: = (A X B) x (A X C) or = do stuff in parenthesis first then cross with A

To cube the matrix [A] I assume you square it and then multiply the result by [A] however in matrix multiplication order matters: so which is correct? [A]^3 = [A]^2[A] or [A][A]^2