If `theta_1` and `theta_2` be the apparent angles of dip observed in two vertical planes at right angles to each other, then show that the true angle of dip, `theta` is given by `cot^2theta=cot^2theta+cot^2theta`.
A. `cot^(2) theta = cot^(2) theta_(1)+cot^(2) theta_(2)`
B. `tan^(2) theta= tan^(2) theta_(1) + tan^(2) theta_(2)`
C. `cot^(2) theta= cot^(2) theta_(1) -cot^(2)theta_(2)`
D. `tan^(2) theta=tan^(2) theta_(1)-tan^(2)theta_(2)` .
