- #1

asi123

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## Homework Statement

Hey guys.

So I've got a current which goes through an infinite wire and I need to find the magnetic field which is caused by the wire at point P.

I used the Biot–Savart Law and in the picture you can see what I came up with (sorry, no scanner today, I had to do it the short way ).

So, my question is, how am I suppose to get from the green equation to the red one? I took the red equation from their answers.

Am I missing something?

Thanks.