A Satellite Passes Over Two Tracking Stations $$A$$ And $B$ $100$ Km Apart When the Satellite Is Between the Two Stations the

Essay

A satellite passes over two tracking stations, $$A$$ and $B$ , $100$ km apart. When the satellite is between the two stations the angles of elevation at the stations are measured as $89 ^ { \circ }$ and $87 ^ { \circ }$ respectively. What is the distance, $a$ between the satellite and station $B$ .