def calc_dewpoint(temp, hum):
    '''
    calculates the dewpoint via the formula from weatherwise.org
    return the dewpoint in degrees F.
    '''

    c = fahrenheit_to_celsius(temp)
    x = 1 - 0.01 * hum;

    dewpoint = (14.55 + 0.114 * c) * x;
    dewpoint = dewpoint + ((2.5 + 0.007 * c) * x) ** 3;
    dewpoint = dewpoint + (15.9 + 0.117 * c) * x ** 14;
    dewpoint = c - dewpoint;

    return celsius_to_fahrenheit(dewpoint)
calculates the dewpoint via the formula from weatherwise.org
    return the dewpoint in degrees F.