An airplane is approaching an airport at an altitude of 300 feet. Looking directly down the runway, the pilot sights an angle of depression with a measure of 29 degrees to the near end of the runways, and one with a measure of 7 to the far end of the runway.
Let the perpendicular line dropped drawn from the airplane to ground meet at C. If the airplane is A, the start of the runway B and the end of the runway D, we have two right triangles, ACB and ACD.
The length of the runway is DC - BC = `300/tan 7 - 300/tan 29`
= `300*(1/(tan 7) - 1/(tan 29))`
`~~ 1902.08` feet
The length of the runway is approximately 1902.08 feet