# calculus

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QUESTION 3

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 -

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(t-3))^2
2d dd/dt = 200(t-3)
at t=7, d=50
2*50 dd/dt = 200(4)
dd/dt = 8 mph

• calculus -

i'm still not understand for this conclution

• calculus -

*conclusion not conclution

• calculus -

where do you get 200(t-3)???

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