# math

a boat crosses a river and arrives at a point on the opposite bank directly across from its starting position. The boat traveks at 4m/s and the current is 2m/s. If the river is 600 m wide in what direction must the boat steer and how long will it take to cross?

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1. current toward -y
We want to go in +x direction
steer at angle T up from x axis

components toward x
Vx = 4 cos T
components toward y
Vy = 4 sin T - 2

we want Vy = 0
so
2 = 4 sin T
sin T = 1/2
T = 30 degrees or in compass heading
30 degrees North of East = 60 degrees true

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