Hello,

d^2F = k* \frac {i_1*\vec{dl_1} \times (i_2*\vec{dl_2} \times \vec{r})}{r^3} \ => \ \frac{k}{|r|^2} * i_1\vec{dl_1} \times i_2\vec{dl_2} \times \hat{r}



GIVEN: i_1=1; \ i_2=1; \ |r|=1; \ \hat{r}=[0,-1,0]; \ \vec{dl_1} \parallel \vec{dl_2}
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d^2F = k/1^2* 1*[dl_1,0,0] \times 1*[dl2,0,0] \times [0,-1,0]

Code:
D[k/1^2 * 1*{l1,0,0} cross 1*{l2,0,0} cross {0,-1,0}, l1,l2]
EXECUTE HERE: Wolfram|Alpha --> F= [0, k, 0] \ ??


Is that correct result? How to write this in integral form?