| 32 | |
| 33 | So our integral is now |
| 34 | |
| 35 | $\int f( \sqrt{x_i^2+\left(s \cos(\theta) \right ) ^2}, y_i+s \sin(\theta), 0 ) ds$ |
| 36 | |
| 37 | |
| 38 | Now, if $\theta = 0$, this simplifies to |
| 39 | |
| 40 | $\int f( \sqrt{x_i^2+s ^2}, y_i, 0 ) ds$ |
| 41 | |
| 42 | and we can undergo a chance of variables |
| 43 | |
| 44 | $ x' = \sqrt{x_i^2+s^2}$ |
| 45 | |
| 46 | and |
| 47 | |
| 48 | $dx' = \frac{s}{\sqrt{x_i^2+s^2}} = \frac{\sqrt{x'^2-x_i^2}}{x'} ds$ |
| 49 | |
| 50 | so our integral becomes |
| 51 | |
| 52 | $2 \int_{x_p}^{\infty} f( x', y_i, 0 ) \frac{x'}{\sqrt{x'^2-x_i^2} } dx'$ |
| 53 | |
| 54 | |
| 55 | and $B_\perp$ is unchanged, while $B_x = B_\phi \cos(\theta) = B_\phi \frac{x_i}{x'}$ |
| 56 | |
| 57 | |
| 58 | |
| 59 | |
| 60 | [[CollapsibleStart]] |