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Ryan, Engineer
Category: Math Homework
Satisfied Customers: 7011
Experience:  B.S. in Civil Engineering
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# Let c be a non-zero constant let f : R^4 -> R be the function f(x,y,z,t)=sin(x-ct)+s

### Resolved Question:

Let c be a non-zero constant let f : R^4 -> R be the function

f(x,y,z,t)=sin(x-ct)+sin((3/5)y + (4/5)z - ct)

Show that the following partial derivatives:

fxx + fyy + fzz - (1/c^2)*ftt = 0
Submitted: 5 months ago.
Category: Math Homework
Expert:  Ryan replied 5 months ago.
Hi,

Welcome! Thank you for your question.

I'll have the solution for this posted for you shortly. I have it worked out, I just need to type it up.

Thanks,

Ryan
Customer: replied 5 months ago.

Thanks, XXXXX XXXXX pretty quick, which obviously doesn't speak volumes of my expertise in multivariable calculus

Cheers

Expert:  Ryan replied 5 months ago.
Hi,

Here is the solution:

PartialDerivatives

Multivariable calculus can be confusing, especially when you are just starting out. Please don't hesitate to ask if you have any questions about the solution. I'll be happy to explain anything that is not clear.

Thanks,

Ryan
Customer: replied 5 months ago.

You're a freaking GOD in calculus.

I've been looking for days for related online material but couldn't find any.

If you just happen to know of any good resource containing similar problems that would be double awesome.

Cheers

Expert:  Ryan replied 5 months ago.
Hi,

Well, shucks...

Thank you.

Off the top of my head, I don't know of any specific sites that would include examples, but a quick Google search brought up this one:

http://mathinsight.org/partial_derivative_examples

You might also want to see if Kahn Academy has any videos that you can use on this subject. Here is one possibility:

You can also find some explanation of partial derivatives here:

http://tutorial.math.lamar.edu/Classes/CalcIII/PartialDerivatives.aspx

And if none of that does the trick, I'll be happy to write up some example problems for you.

Hope this helps.

Regards,

Ryan
Ryan, Engineer
Category: Math Homework
Satisfied Customers: 7011
Experience: B.S. in Civil Engineering

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