The angle of elevation of a tower of height h from a point A due South of it is x and from a point B due East of B is y. If AB = z, then which one of the following is correct?

• A. h2 (cot2 y + cot2 x) = z2
• B. z2 (cot2 y – cot2 x) = h2
• C. h2 (tan2 y – tan2 x) = z2
• D. z2 (tan2 y – tan2 x) = h2