If $\theta_1$ and $\theta_2$, be the apparent angles of dip observed in two vertical planes at right angles to each other, then the true angle of dip 0 is given by :

Question

$\begin{array}{1 1} (1) \cot^2 \theta= \cot^2\theta_1+\cot^2\theta_2 \\ (2) \tan^2 \theta= \tan^2\theta_1+\tan^2\theta_2 \\ (3) \cot^2 \theta= \cot^2\theta_1-\cot^2\theta_2 \\ (4) \tan^2 \theta= \tan^2\theta_1-\tan^2\theta_2\end{array}$