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Help me! On the east-west coastline L, there is a wharf MN…… with the length of 1 km (math problem in Grade Three).
: (1) According to the meaning ∠ BAC = 90

BC=√[40? +(8√3)? ]= 16√7

Ship speed =16 √ 7/(4/3) =12 √ 7 km/h.

(2) In the coordinate system as shown in the figure.

B(-20,20√3)C( 12,4√3)

Let a straight line lbc: y = kx+b.

Substitute the coordinates of b and c into y = kx+b.

Get -20k+b=20√3。

12k+b=4√3

The solution is k =-3/2 b =10 √ 3.

∴ Linear LBCY =-3/2x+10 √ 3

When y=0, x=20 is E (20,0).

∫M( 19.5,0),N(20.5,0)

If the ship continues to sail and does not change its course, it can directly dock in MN.