Where is this term coming from?

[bigmike94]

TL;DR

I am back again to ask for your mathematical help.

I got the same result apart from that extra x in the second term? I have boiled it down to that it must have come from maybe the x hat j hat and z hat part of the product rule? Any help would be grateful thank you!

 

[anuttarasammyak]

It comes from numerator of the formula above, x i-hat.

 

[PeroK]

@bigmike94 can you write down what $A_x$ is?

 

[bigmike94]

It comes from numerator of the formula above, x i-hat.

Yeah I had a guess what assumed that was it but why is it included and not y or z aswell? Maybe I am missing an i hat which will get rid of the j and z hat cos of the dot product?

 

[bigmike94]

@bigmike94 can you write down what $A_x$ is?

I’m not sure how to type maths in here but I think you have just helped me crack it, because it’s in the x direction only we ignore y hat and z hat, then In the product rule you’re left with the extra x.

I’m not sure if that makes sense to you? But yeah I think I get it now thank you

 

[PeroK]

I’m not sure how to type maths in here but I think you have just helped me crack it, because it’s in the x direction only we ignore y hat and z hat, then In the product rule you’re left with the extra x.

I’m not sure if that makes sense to you? But yeah I think I get it now thank you

By definition $$\vec A = A_x \hat i + A_y \hat j + A_z \hat k$$This can also be expressed as:$$A_x = \vec A \cdot \hat i$$

You need to learn some LaTex:

https://www.physicsforums.com/help/latexhelp/