Posted by meen on .
A boat sails 30 miles to the east from a point P, then it changes direction and sails to the south. If this boat is sailing at a constant speed of 10 miles/hr, at what rate is its distance from the point P increasing
a) 2 hours after it leaves the point P
b) 7 hours after it leaves the point p

calculus 
Steve,
at 10 mph, it is still going east at t=2
so, distance is increasing at 10 mph
at t=3, it turns south. After that, the distance d from P is
d^2 = 30^2 + (10(t3))^2
since it has only been sailing south for (t3) hours.
2d dd/dt = 200(t3)
at t=7, d=50
2*50 dd/dt = 200(4)
dd/dt = 8 mph