(a) The demand curve facing a monopolist is downward sloping as he can expect to sell more by reducing the price. This is shown in the diagram. The monopolist sells OM quantity at OP price. If he wants to increase his sales by MM1 he can do this by reducing price by PP1, as a fall in price will cause an increase in quantity demanded.
(b) The demand curve under monopoly is also very steep, that is, the demand curve DD in the diagram is in-elastic due to the absence of close substitutes.
