To approach the runway, a pilot of a small plane must begin a 15 degree descent starting from a height of 2530 feet above the ground. how many miles from the runway is the airplane at the start of the approach

1. Let A represent the initial position of the plane and C the runaway (check the picture at the bottom of the answer).

2. The angle shown in the circle and angle C are alternate internior angles, or Z angles, so the measure of angle C is 15°.

3. 

4. Angle 15° is generally handled with half angle formulas, we have 



so 



5. Another way is to use a trigonometric values calculating software.

6. Thus,