<PRE><B>Question 900494</B>
Two railroad tracks intersect at right angles at station O. At 10AM the train A, moving west with constant speed of 50 km/h, leaves the station O. One hour later train B, moving south with the constant speed of 60 km/h, passes through the station O. Find minimum distance between these trains
-----------------
t = 0 at 1000
{{{s = sqrt((50t)^2 + (60 - 60t)^2)}}}
{{{s = sqrt(2500t^2 + 3600t^2 - 7200t + 3600)}}}
{{{s = sqrt(6100t^2 - 7200t + 3600)}}}
ds/dt = (1/2)(12200t - 7200)/sqrt(6100t^2 - 7200t + 3600)}}} = 0
12200t = 7200
t = 0.59016 hours past 1000
t =~ 10:35:24.6
=====================
At that time,
s =~ 38.411 km




</PRE>