Respuesta :
Answer:
DL/dt = 1000 miles/hour
Step-by-step explanation:
Let´s call A Point for the airplane at 70 miles from the point O (converging point), and point B for the airplane at 240 miles from point O.
Then the three-points A, B, and O shape a right triangle with legs (distances from each of the airplane to point O, and hypotenuse L distance between the two airplanes
Then according to Pithagoras´theorem:
L² = (AO)² + (BO)²
At the moment t when the airplanes are far away as 70 and 240 miles per hour
L² = (70)² + ( 240)²
L² = 4900 + 57600
L = √62500
L = 250 miles
In general
L² = x² + y²
That equation is always valid for a right triangle if the airplanes are approaching keeping the right triangle shape then:
L² = x² + y² where x and y are the legs ( that legs change in time then):
Tacking derivatives on both sides of the equation
2*L*DL/dt = 2*x*Dx/dt + 2*y*Dy/dt
By substitution: since Dx/dt = 280 m/h and Dy/dt = 960 m/h
2*(250)*DL/dt = 2*70*280 + 2*(240)*960
500*DL/dt = 39200 + 460800
DL/dt = 500000/ 500
DL/dt = 1000 miles/hour
