Mathematical economics
Appearance
Mathematics and Economics are totally linked. For instance, one can use differentiation and integration to find the Elasticities of Demand and Supply.
Following are a few examples:
If the total cost of the firm is given by TC(x) = x3 + 5x + 6 and the target is find the Marginal Cost.
Then take the derivative of TC with respect to x i.e. d(TC)/dx = 3x2 + 5. This is the cost of producing one additional unit of output (from x to x+1).