In the Linear Demand Curve AB, the elasticity of demand $(e_D)$ at point D can be measured  geometrically by the formula.

$e_D=\frac{DA}{DB}$ $e_D=\frac{DB}{DA}$ $e_D-=\frac{BK}{KA}$ $e_D=\frac{KA}{BK}$

$e_D=\frac{DA}{DB}$

The correct answer is option (1) : $e_D=\frac{DA}{DB}$