The demand curve cannot be of a rectangular shape since that would imply that the demand is the same at two different price levels even though other factors remain the same.
what will be the shape of indifference curve if one of the two goods is a free commodity
The demand curve faced by a pure monopolist is of downward sloping in shape.
Usually market demand curves are downward sloping.
Usually market demand curves are downward sloping.
We have seen already that demand curves (price Demand) slope downwards from left to right. Since demand curve is only a geometrical representation of the law of demand with 'quantity' on the X axis, and 'price' on the Y axis, the shape of the demand curve has to be necessarily of one sloping downwards showing that more is demanded at a lower price. The question why does the demand curve slope downwards is an indirect way of asking why does the law of demand operate. What are the reasons behind the operation of law of demand? why do people demand more if price comes down? So it is better to discuss the reasons behind the law of demand or the economics of law of demand in order to understand the question under discussion.
The shape of a unit elastic demand curve for a product is influenced by factors such as the availability of substitutes, the necessity of the product, and the proportion of income spent on the product.
It is a slope that goes downwards from left to right.
The shape of the market demand curve for a public good is influenced by factors such as the level of individuals' willingness to pay for the good, the number of people who benefit from the good, and the availability of substitutes for the good.
The demand curve in a perfectly competitive market is U-shaped owing to the fact that as the economies of scale take effect average costs begin to lower down. Finally though, the diseconomies of scales take effect too thereby causing the average costs to go up hence creating a u-shape for the demand curve.
Because it is basically curved shape, therefore, there are points/areas on the curve where the demand or supply will be elastic and on some other parts be inelastic. At the top of the curve, demand/supply tends to be inelastic and at the bottom of the curve, it tends to be elastic. Obviously, the more you go up the more we reach the perfectly inelastic demand/supply and the further you go down the curve, the more you reach the perfectly elastic demand/supply
a shape that is rectangular so deal with it
I have never heard that the demand curve must be concave. In fact, it is most often modeled as either linear or convex. Common convex specifications include log-linear and constant-elasticity demand functions. A number of empirical papers attempt to estimate the shape of the demand curve for specific products but I am not familiar with anyone concluding that demand is concave generally.