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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def dxdy(line):
 """ return normalised ascent vector """

    x0, y0, x1, y1 = line
    dx = float(x1 - x0)
    dy = float(y1 - y0)
    f = hypot(dx, dy)
    return dx / f, dy / f