Elasticity can be greater than, less than, or equal to 1. If ed tends to infinity , demand is perfectly elastic . Elasticity is NOT equal to slope. Recall we need the percentage changes. To find a value for the elasticity that is independent of the direction of change, i.e. A to B or B to A, use the midpoint formula.
Elasticity usually changes along a demand curve - even when the demand curve is a straight line.
For prices greater than the price at the midpoint, demand is elastic , for prices less than the price at the midpoint, demand is inelastic. A perfectly horizontal demand function is perfectly elastic. A perfectly vertical demand function is perfectly inelastic. According to the law of demand, if price increases quantity decreases. It depends on the elasticity.