Two planes leave an airport at the same time, one flying at 300 km/h and the other at 420 km/h. The angle between their flight paths is 75 degrees. After three hours, how far apart are they?

From the top of a building 10 m tall, the angle of elevation to the top of a flagpole is 11 degrees. At the base of the building, the angle of elevation to the top of the flagpole is 39 degrees. Find the height of the flagpole.

In quadrilateral ABCD, AB=3, BC=4, CD=5, and DA=6. The length of diagonal BD is 7. Find the length of the other diagonal.