Answer: Solution: The points B are BE⊥CD and BF⊥AD respectively, and the vertical feet are E and F respectively.

Let BC = XM.

∫∠CBE = 60，

∴BE= 12x,CE=32x.

CD = 200，

∴DE=200-32x.

∴BF=DE=200-32x,DF=BE= 12x.

∫∠CAD = 45，

∴AD=CD=200.

∴AF=200- 12x.

At Rt△ABF, tan 30 = bfaf = 200? 32x200？ 12x，

The solution is x = 200 (3- 1) (m).

Answer: Cable BC is at least (2003-200) meters.