Why demand curve under monopolistic competition is more flatter?
Under a monopolistic competition, the products of different firms are close substitutes of each other. The products are very much similar to each other and perform the same basic function. This suggests that with a slight increase (or, decrease) in the price of the product, demand of the product would decrease (or, increase) by a large extent. It is due to this fact that the demand curve faced by a seller under monopolistic competition is flatter.
Because in a monopolistic competiton a good has many close substitutes whereas in a monopoly a good doesnt have any substitute .
thus,in a monopolistic competition the demand for a good in highly elastic (flatter demand curve) and in monopoly the demad for a good is inelasic (steeper demand curve )