def calc_humidity(temp, dewpoint):
    '''
    calculates the humidity via the formula from weatherwise.org
    return the relative humidity
    '''

    t = fahrenheit_to_celsius(temp)
    td = fahrenheit_to_celsius(dewpoint)

    num = 112 - (0.1 * t) + td
    denom = 112 + (0.9 * t)

    rh = math.pow((num / denom), 8)
    
    return rh
calculates the humidity via the formula from weatherwise.org
    return the relative humidity