call eastward plane A and westward plane B
speed from west is 450
speed from south is 275
the distance between them is defined by pythagorean theorem
where s is distance between
when sA=sB=100, then find speed of change in distance
first find distance


if we look at
and take the derivitive of both side with respect to time, we get

is speed of plane A
is speed of plane B
we are solving for

subsituting

solving