Source: Graphs by Justin Tapp
The middle point that represents the average of price and supply when determining price elasticity.
(QA-QB) / (QA+QB)
(PA-PB) / (PA+PB)
Arc Price Elasticity
Dividing the percent change in quantity by the percent change in price to analyze the relationship between the two economic variables.
Elasticity of demand when the price of a good changes, keeping all other variables and goods separate.