Question 142612
You can use the Tangent function to solve this problem.
Imagine a right triangle whose height (h) represents the altitude of the aeroplane (0.75 miles) and whose base repesents the ground distance from the present position of the plane (on the ground) to the start of the airport runway (x miles).
The 4 degree descent is the angle between the base and the hypotenuse of the right triangle.
The tangent of the 4 degree-angle is given by h/x, or:
{{{tan(4) = h/x}}} Substituting h = 0.75 and tan of 4 degrees = 0.07, then...
{{{x = 0.75/0.07}}}
{{{x = 10.7}}}miles.