The slope of the demand curve is dP/dQ, and the elasticity is (dQ/dP)P/Q, and the elasticity is the reciprocal of the slope multiplied by the final P/Q, but in the case of economics, the horizontal axis is the quantity and the vertical axis is the price, which is contrary to mathematics, so the slope of the demand curve in economics is the reciprocal of the slope in mathematics, that is to say, its elasticity is the slope multiplied by P/Q.

Price elasticity of demand:

Short for price elasticity or demand elasticity, demand price elasticity: refers to the reaction degree of demand to price change, which is the percentage of demand change divided by the percentage of price change. The measure of the response degree of demand change rate to commodity price change rate is equal to the demand change rate divided by the price change rate.

Slope of demand curve:

The independent variable x is placed on the vertical axis, and the dependent variable y is placed on the horizontal axis, and the slope =△y/△x= horizontal axis variation/vertical axis variation.

The difference between the elasticity of demand price and the slope of demand curve;

They are mutual.

Basic types of demand price elasticity:

When the change percentage of demand is greater than the change percentage of price and the elasticity coefficient of demand is greater than 1, demand is said to be elastic or highly elastic;

When the percentage of demand change is equal to the percentage of price change and the demand elasticity coefficient is equal to 1, it is called single demand elasticity;

When the change percentage of demand is less than the change percentage of price and the elasticity coefficient of demand is less than 1, it is called inelastic or low elasticity of demand.