State tangent law in magnetism.

Question

$\begin{array}{1 1} \tan \theta = \large\frac{B_1}{B_2} \\ \tan \theta = \large\frac{B_2}{B_1} \\ \tan \theta = \large\frac{R}{B_1} \\ \tan \theta = \large\frac{R}{B_2} \end{array}$