| | 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]] |