<P> If the two inputs are perfect complements, the isoquant map takes the form of fig . B; with a level of production Q3, input X and input Y can only be combined efficiently in the certain ratio occurring at the kink in the isoquant . The firm will combine the two inputs in the required ratio to maximize profit . </P> <P> Isoquants are typically combined with isocost lines in order to solve a cost - minimization problem for given level of output . In the typical case shown in the top figure, with smoothly curved isoquants, a firm with fixed unit costs of the inputs will have isocost curves that are linear and downward sloped; any point of tangency between an isoquant and an isocost curve represents the cost - minimizing input combination for producing the output level associated with that isoquant . A line joining tangency points of isoquants and isocosts (with input prices held constant) is called the expansion path . </P> <P> The only relevant portion of the isoquant is the one that is convex to the origin, part of the curve which is not convex to the origin implies negative marginal product for factors of production . The higher the isoquant, the higher the production . </P>

Set of isoquants presented on two dimensional plain is referred as