A rough sketch will often clear the fog.
The assumption is that the "57 feet downhill" is measured along the slope of the ground (and not horizontally from the base of the pole.)
The "point" will be
feet BELOW the base of the pole; add that to the 34 feet to get the altitude of the triangle.
55.5 feet away from the center of the vertical pole; this is the base of the triangle.
the length of cable required = is the hypotenuse of the triangle.
Does that help?