Here's a calc III problem(that was my approach) if anyone would like a shot. Not particularly difficult but kind of interesting.

"An airplane approaches the end of a runway from the east with an angle of 20 degrees. A tower 50 feet high is located 400 feet south and 800 feet east of the runway. How close does the plane come to the top of the tower?".

Here's a 'paint' drawing. It's a little tilted, but it should suffice.